mucous membrane, and when removed leaves a raw, bleeding surface. Sections through this exudate and the subjacent tissues show that the epithelial layer is destroyed, and the underlying tissue infiltrated with cells. The extent of the infiltration varies in different individuals. (Fowl 59, Outbreak I.)

(3) The mucosa is covered with a thick mass of exudate, varying in color from a milky white to a lemon yellow or brown. It is easily removed, leaving a more or less granular and healed surface. This sloughed mass is frequently dried at its margins to the adjacent tissue. It emits a strong putrid odor, due to decomposition. The drying of the margins prevents the fowl from expelling the exudate after it becomes separated from the underlying tissue. (Fowl 63, Outbreak V.)

The evidence to support the supposition that the three forms or types of exudate described are different stages in the same morbid process, as gathered from the post-mortem notes and bacteriological study of the cases here reported, may be summarized as follows:

(a) Abnormal conditions, representing the intermediate and. connecting links between the specific types of lesions, were frequently encountered.

(b) Although but one form of exudate was usually present in a single fowl, there were marked exceptions, in which two, and in one case the three, forms were coincident. Thus in fowl No. 75 (Outbreak III) the eye was covered with a sloughed exudate. In the posterior nares there was a layer of muco-purulent substance, and on the mucosa of the mouth were areas of a diphtheritic exudate. Fowls Nos. 69 and 73 furnish examples where the diphtheritic process and the sloughed exudates were present.

(c) The same species of a pathogenic bacillus was associated with each form of exudate. It was almost invariably found with the first and second, but rarely with the third.

In the fowls which died, the exudates were for the greater part in the advanced stage, although there were several fatal cases in which the lesions were restricted to an abnormal quantity of a serous or mucopurulent, more or less viscid, exudate in the conjunctiva or nasal cavities. The best illustration of the diphtheritic process was found in certain of the fowls killed for examination.

The distribution of the lesions shows that the conjunctiva was most frequently affected. The exudate in the nasal cavities was in a few cases undoubtedly the result of the coagulation of the liquid which had passed during the course of the first stage from the conjunctiva through the lachrymal duct into the nares. In certain of the other cases, how ever, the lesions appeared in the nares only (fowls Nos. 3, 4, and 5). Inadvertently, in these cases no material for sectioning was saved from the mucosa of the nares or conjunctiva. Sections of the exudate, with subjacent tissue from the cornea and the mouth, show that there is a cell

infiltration into the mucosa which destroys the epithelial layer and frequently the submucous tissues to a considerable depth. (See Pl. VI.) The fact should not be overlooked, as pointed out in the post-mortem notes, that the disease in the eye was confined to the conjunctiva and the cornea, the posterior portion remaining apparently normal. Although the lesions were found more frequently in the eye, the number of fowls examined was not large enough to admit of the conclusion that this is generally the case.

From the observations thus far made the provisional theory is entertained that the three forms of the exudate-serous or muco-purulent, diphtheritic, and sloughed mass-represent three stages in the course of the same disease. It is easily understood that fowls examined in the first stage would be said to be affected with a catarrhal condition of the mucosa of the eyes or nares. It is highly probable that in many cases the disease never reaches the second stage (see fowls Nos. 3, 4, 5, and 71), and if these cases alone were examined the diphtheritic condition would not be suspected. It appears, however, that in the majority of cases the disease runs its course, and membranes are formed, slough, and recovery follows. It is further presumable that the disease in question appears sometimes in a virulent and destructive form. I am in possession of statements from poultry raisers which show that there are occasionally epizootics of a disease characterized by exudates in the eyes, nose, or mouth, which runs a rapidly fatal course. It appears that it is such outbreaks which have been reported in Europe as diphtheria, and not the low form of chronic disease which I have encountered.

It is highly probable that there are many affections of fowls resembling somewhat closely the lesions found in the cases examined which are etiologically different. There is much doubt respecting the cause of the apparently sporadic cases of this disease. Whether they differ other than in the degree of virulence of the specific organism from the rapidly fatal disease sometimes reported can not be determined until such epizootics can be thoroughly studied. It is hoped that the investigation of this disease or class of diseases may be continued until the doubtful points concerning their nature and cause are clearly explained, and efficient methods of prevention and treatment are determined.

BACTERIA ASSOCIATED WITH THE LESIONS.

It has already been shown that bacteria were not found in the internal organs or blood of the affected fowls when they were examined before post-mortem changes occurred. It has also been stated that a nonmotile, pathogenic bacillus was found associated with the lesions, especially in the first and second stages, in a considerable number of the fowls.

The examination of the exudates for bacteria was attended with many difficulties, owing to the presence of a large number of sapro

phytes. The method found to be the most trustworthy for the isolation of the pathogenic bacteria was the subcutaneous inoculation of experimental animals with the exudates. If the inoculated animals died, pure cultures of the pathogenic organism were obtained from the blood, liver, or spleen. If they survived, they were subsequently chloroformed and cultures of the parasitic bacteria obtained from the tissue at the point of inoculation. By this process the saprophytes were destroyed in the tissues and only those organisms encountered which were suspected to be of more or less etiological importance.

The success of the animal inoculation over the culture methods in isolating the nonmotile pathogenic bacillus is explained from the fact that it is not vigorous in its growth on culture media and that it was ordinarily crowded out by more vigorously growing saprophytes. It is further presumable that in the older exudates its virulence is gradually lost (see fowls Nos. 1 and 59), so that its presence could not be detected readily by animal inoculation. If rabbits had been inoculated, however, with large quantities of the exudate from the more advanced disease a few additional cases containing the pathogenic-but attenuated-bacillus would undoubtedly have been found. The severe local lesions produced in rabbits by the injection of such material caused them, with few exceptions, to be abandoned. It is evident, in view of the results obtained, that rabbits were the most efficient experimental animals to use in this work, and that fowls were the most refractory. The scarcity of rabbits, however, led to the use of other animals in a few cases.

Cover-glass preparations made from the lesions of the affected fowls were carefully stained and examined. Those prepared from the surface of the exudate and from the necrotic masses generally contained innumerable bacteria, but no predominating species was observed. Similar preparations from the base of the exudate in the more recent stages contained a large number of short bacilli with the ends rounded. These forms frequently exhibited a polar stain. Several preparations were

A large number of species of bacteria were isolated and studied somewhat carefully. Among them are several quite interesting forms, some of which were suspected to be of more or less economic importance. Prominent among these was a bacillus which resembled morphologically and in certain of its cultural characters the bacillus of tuberculosis. It was not pathogenic for guinea-pigs or fowls, and did not take the Koch stain.

2It is of interest to note that several varieties of colon bacteria were isolated in this way. One of these possessed such variations from the colon bacillus in its cultural manifestations and it was possessed of such marked pathogenesis that for a time it was suspected of bearing some causal relation to the disease. It was briefly described in a footnote on page 43.

3 In both fresh and stained preparations a long spirillum was found to be quite abundant. It was from 2 to 4 u in length. Thus far I have been unable to detect it in artificial cultivations.

stained for tubercle bacilli, but with negative results. A summary of the results obtained from animal inoculations is appended in tabulated form

Rabbit No. 117... Eye, fowl No. 1..... Dec. 28, 1893 Died Feb. 10, 1894. Rabbit very much emaci

Rabbit No. 223... Eyes, fowl No. 71... Nov. 5, 1894 Found dead Dec.

19, 1894.

Rabbit No. 226... Nares, fowl No. 75.. Nov. 22, 1894 Found dead Nov.

23, 1894.

Do.
Do.

Pleuritis; hemorrhages in the intestines; noumotile pathogenic bacillus. Pleuritis and peritonitis; nonmotile pathogenic

bacillus.

Septicæmia; nonmotile pathogenic bacillus.

The table shows that the pathogenic bacillus was obtained from the lesions of fowls Nos. 1, 3, 4, 5, 59, 69, 71, and 75, or nearly 50 per cent of those examined. It is a significant fact that the bacillus was obtained from all the fowls but one (No. 61) where the lesions either in the eye, nares, or mouth were not far advanced. In one case (No. 73) no inoculations were made. The almost constant appearance of this bacillus in the more recent lesions renders the apparent small percentage of cases from which it was isolated of much greater importance than it would at first be considered. A comparative study of the bacteria from the different fowls showed that those obtained from fowls Nos. 1, 59, 69, and 71 were attenuated in varying degrees, while those from the other cases were sufficiently virulent to destroy rabbits within twenty-four hours. This variation in the degree of virulence of the cultures obtained from different fowls is interesting and important. There was no difference in their cultural characters. A glance at the post-mortem notes will show that in the fowls from which the attenuated forms were obtained the lesions were apparently older or more advanced than in the other cases.

In previous investigations rabbits were inoculated with the nasal and pharyngeal secretions of several healthy fowls. These rabbits

1 Bulletin No. 3, Bureau of Animal Industry, 1893, p. 47.

remained perfectly well. Although septic bacteria are known to be common in the secretions covering the normal mucosa of the upper air passages of several species of domesticated animals, such organisms have not been reported from the mucosa of healthy fowls.

In 1890 two fowls' which died very suddenly at the experiment station of this Bureau were examined. One of them exhibited a croupous exudate extending from the larynx into the trachea, and the other a swollen condition of the mucosa of the mouth and œsophagus. No pathogenic bacteria were obtained from the fowl suffering from the exudate, but from the other were obtained pure cultures of a bacillus not distinguishable from that of swine plague.

It is impossible to positively identify the pathogenic bacillus found associated with the lesions in this disease with the one described by European writers as the cause of fowl diphtheria. Morphologically it is similar to the one described by Loeffler, but its pathogenesis is different. This may be due, however, to difference in the degree of virulence. There is much obscurity in the reference to the properties of the bacilli found by other investigators as the probable cause of diphtheritic affections of fowls and birds, as their descriptions are exceedingly meager, being often limited to the morphology and possibly the character of the growth on one or two of the more commonly used culture media.

In those species of pathogenic bacteria which have been more fully described a more accurate comparison is possible. Thus, the bacilli of fowl cholera, swine plague, and rabbit septicaæmia are found to be comparable with the bacillus about to be described, and found in the lesions of this disease of fowls. While it is not my purpose to discuss at this time the identity or relationship of these bacteria, it is important to know that a bacillus associated with the peculiar lesions of this disease should be so similar to the one described by European writers as the cause of fowl cholera. The more essential properties of the bacillus found, apparently the etiological factor, in the lesions of the diphtheritic disease of poultry which I have studied are appended:

DESCRIPTION OF THE NONMOTILE PATHOGENIC BACILLUS.

Morphology.-A nonmotile, rod-shaped organism 0.8 to 1.5 μ long and from 0.8 to 1.2 thick. The ends are oval, and the shorter forms appear to be nearly spherical. In bouillon they are frequently in short chains and in clumps. When stained with the aniline dyes in cover-glass preparations made directly from animal tissues they exhibit a light center, occasionally showing deeply stained poles. In preparations from cultures this character is much less marked. No capsule has been positively demonstrated, although certain preparations suggest its existence. It stains readily with the aniline dyes ordinarily used. It does not retain the coloring matter when treated after the Gram method.

Culture characters.-On agar at 36° C. the growth is not vigorous. It is of a neutral gray color, with a glistening, moist-appearing surface. The growth is slightly viscid, and adheres quite firmly to the agar surface. The condensation water becomes

Special Report on Swine Plague, Bureau of Animal Industry, Department of Agriculture, 1891, p. 158.