86 . MICHIGAN ACADEMY OF SCIENCE. 



PAPERS EEAD IX THE SECTION OF SANITARY SCIENCE. 



THE STUDY OF AN EPIDEMIC AMONG GUINEA PIGS. 



(Abstract.) 

 BY L. M. GELSTOX. 



In January, 1901, the supply of guinea pij-s in the hygienic hiboratory 

 of the University of Michigan being- nearly exhausted, animals were 

 ordered from several different sources and within a few weeks over 

 six hundred guinea pigs were sent to the laboratory. Of these nearly 

 five hundred were received from one source, and among these a ])eciil- 

 iar and highly fatal epidemic soon appeared, and after about three 

 weeks extended to all the guinea pigs kept in the laboratory. The in- 

 fected animals began to emaciate and to lose their hair. They gradu- 

 ally failed and apparently died of inanition. Post-mortem examina- 

 tion was made upon two hundred animals, and in 88.2 per cent of these 

 a certain bacillus was found in the blood of the heart. Post-mortem 

 examination showed the lungs in a pneumonic condition; the serous 

 coat of the intestines, the omentum and the mesenterv markedlv con- 

 gested; the spleen dark and enlarged; slight enlargement of the inguinal 

 and axillary glands, and heart in diastole. The germ found in the blood 

 of the heart is a short bacillus with rounded ends, growing singly or 

 in pairs, rarely in threads. The bacilli are found to be capsulated 

 when seen in the tissues, but not when grown in cultures. This bacillus 

 takes the ordinary anilin stains readily and is exceedingly motile. 

 Spore production has not been observed. In bouillon after twenty-four 

 hours there is an abundant, diffuse growth with the formation of a thin 

 pellicle. After five days the pellicle is found to be greatly increased 

 in thickness and folded on the surface. The growth does not 

 readily subside. This organism does not coagulate milk. In the stab 

 cultures, the growth appears all along the line of inoculation and forms 

 a film over the surface of the medium. In glucose media there is a 

 marked production of gas. Streak cultures on plain agar show a thin 

 film; on glycerin agar the growth is somewhat thicker and pearly white; 

 on blood serum there is a rapidly spreading, moist, thick growth; on 

 potatoes the growth is moist, thick and white. On agar plates the 

 colonies are white and show a nuirked tendency to coalesce on the sur- 

 face. The surface colonies are without distinct borders and are coarsely 

 granular, while the deeper colonies are rounded but somewhat irregular. 



The germ does not liquefy gelatin. This bacillus has its optimum 

 growth at a temperature of from 37.5 degrees to 3!) degrees. It grows 



