cholera. In later years Uhlenhuth and his coworkers reported finding it in the intestinal tracts of many healthy swine. Jordon, in this country, was unable to identify it in any normal hogs which he examined, and neither was Tenbroeck. Both of these investigators regard Uhlenhuth's work as inconclusive owing to the fact that he did not differentiate correctly between B. suipestifer and B. paratyphoid B. Smith states that the only distinction that can be made between the two is that the former is pathogenic for rabbits, while the latter is not.

Rabbits and guinea-pigs succumb to small subcutaneous injections of cultures of B. suipestifer, rabbits being somewhat more susceptible. Swine are not easily infected with subcutaneous injections, but large intravenous doses prove fatal. According to Welch, small doses may lead to formation of the "button ulcers" observed in chronic hog cholera, and Smith secured like results by feeding pigs bouillon cultures.

The part played by this organism in producing swine disease in the field is not well defined, as most work with it ceased as soon as the filterable virus was accepted as the cause of epizoötic hog cholera. There is good evidence that it is one cause of the "button ulcers" just mentioned, and it is likewise probable that, acting in the rôle of secondary invader, it is responsible for the en

larged, dark, and somewhat pulpy spleens observed in individual hogs dead in outbreaks of cholera. It also seems to intensify hemorrhagic lesions produced by the filterable virus. Its pathogenic powers in relation to cholera immune pigs will bear further investigation, but it is probable that for the most part it acts to complicate diseases produced by other causes.

B. pyocyaneus, or, according to Migula's classification, Pseudomonas pyocyaneus, is a motile rod 2 to 6 microns long and .3 to 1 micron broad. It is widely distributed in nature, and there has been a tendency to regard it chiefly as a saprophyte. It is included frequently in the flora of wounds, it appears at times in abscesses in swine and other animals, and it has been described as the cause of an outbreak of dysentery in man. In Germany it is said to be the cause of an infectious nasal catarrh in pigs, and we have found it associated with outbreaks of pneumonia in swine, as the probable cause.

The organism is an aërobe, it grows luxuriantly on the common culture media, tending to overwhelm other bacteria associated with it. It has a marked tendency to produce green color in any culture medium, and the sweetish odor produced by it in bouillon cultures is quite characteristic. It takes the aniline stains regularly, and is Gram negative.

B. pyocyaneus is pathogenic for pigeons, guinea pigs and rabbits. In swine, it is not regularly so, but under certain conditions it assumes great pathogenic significance. We have failed to produce disease by feeding cultures of it or by spraying them into the nostrils of healthy pigs, while subcutaneous doses produced nothing more than an occasional local abscess. Moderate intravenous doses of suspensions containing it cause dyspnea, chilling or spasms to appear immediately, and death, preceded by paralysis, usually of the hind quarters, often takes place in a day or two. This paralysis is observed in rabbits as well, and must be regarded as a more or less constant but nevertheless specific action on the part of the organism. According to Hutyra, cultures of B. pyocyaneus inoculated directly into the ethmoid mucosa in young pigs, produce disease similar to the catarrhal rhinitis observed in Germany.

Under natural conditions certain predisposing factors, among which early age, lung worms, hog cholera virus and long confinement in very dusty quarters are most important, prepare the ground so that B. pyocyaneus exerts its pathogenic powers. We have observed its effects following hyperimmunization during the process of anti-hogcholera serum preparation, the hypers developing a fatal pneumonia in a few days following a large intravenous dose of hog cholera virus.

The lesions produced in swine experimentally infected by means of intravenous injections of material containing B. pyocyaneus are those characteristic of septicemia, congestion and dark coloration of the lymph glands, lungs, kidneys and other organs appearing regularly. We have observed no such effects where natural infection rules. Here the constant lesion produced is pneumonia, acute or chronic, and the constant symptoms that appear are those that may be referred to this condition.

Dyspnea, abdominal breathing and other marked evidence of respiratory distress characterize the disease. Paroxysms of coughing occur when the hog is required to move, the alæ of the nostrils are drawn backward, giving the snout a peculiar pointed appearance, and it is not uncommon for the affected animals to assume a dogsitting position, with the forelegs placed widely apart. Thumping appears frequently. Sometimes there is a yellowish purulent discharge from the nostrils. The appetite may or may not be affected, while the temperature, as a rule, remains normal or is only slightly elevated.

The typical lesion which we have found associated with natural infection due to B. pyocyaneus consists of a semi-chronic type of bronchopneumonia, affecting first the ventral and cephalic portions of the lungs, or if lung worms are pres

ent, the posterior border of the diaphragmatic lobe as well. The solidified portions may be red but are often rather light in color, macroscopically resembling the surface of a salivary gland. There is a marked tendency for necrosis to develop from numerous foci, and multiple abscesses occur, appearing as slightly elevated yellow areas dotted over the surface of the pneumonic lung. Pleuritis is somewhat constant, and a high degree of emphysema appears in the dorsal nonpneumonic portion, giving it a pale white color as compared to the normal pink. Often there is distinct evidence that as a final cause of death an acute pneumonia is superimposed over a more chronic type, in which cases all parts of the lungs are pneumonic, while the lesions in the dorsal and posterior portions are of more recent origin.

B. necrophorus is another organism that sometimes complicates hog cholera. Although subject to wide variations in form, it usually appears as a long, slender, nonmotile rod. It is a strict anaërobe, it stains with the ordinary aniline dyes, and is Gram negative. Evidently it is quite widely distributed in nature, for it appears in numerous necrotic lesions in practically all domesticated animals. It is regarded as a normal inhabitant of the intestinal tract in swine, and it exists in soil contaminated with manure. It is the exciting cause of calf diphtheria, lip and leg ulceration in sheep,