142 EEPOET OF THE BUKEAU OF ANIMAL INDUSTRY. 



This case is chiefly of value in showing that the disease was limited 

 to the thoracic cavity. Th e infection, introduced most likely through 

 the air passages into different regions of the lungs, caused at the 

 places of deposit pneumonia, resulting in direct necrosis or in cell 

 infiltration (catarrhal pneumonia, broncho-pneumonia) and subse- 

 quent caseation. The pleura were at the same time involved by ex- 

 tension of the disease process. The animal had recovered from the 

 attack, so far as recovery was possible, with a lung riddled with cavi- 

 ties and firmly bound to the chest wall. It would have been very 

 desirable to determine by inoculation into rabbits whether the cheesy 

 contents of the lung cavities still contained the living germ, but this 

 was impracticable at the time. 



Some additional statistics on the spread and severity of the same 

 epizootic around Mason City were kindly furnished by Mr. L. M. 

 Van Auken. On December 1, the first farm north of the one desig- 

 nated as Farm C in the preceding pages was overtaken by the disease. 

 Of 14 old hogs and 62 shoats, weighing from 150 to 220 pounds, 2 

 old ones and 24 shoats succumbed up to the 1 second week in January. 

 The animals when overtaken by the plague were kept in a yard of 

 about 1 acre and fattened on soft corn. A farm north of the latter 

 was subsequently infected. After 5 or 6 had died the rest were 

 shipped. One of the dead animals was examined by the owner, and 

 the lungs said to have been very badly diseased. Other herds in the 

 same vicinity were swept away at nearly the same time. 



Most of these farms were visited by the plague for the first time 

 last fall. The disease is said to have been introduced through hogs 

 taken from the stock-yards in January, 1888. The disease seems to be 

 as virulent as hog cholera, and is to be dreaded as much as the latter 

 disease, considering the rapidity and certainty with which it spread 

 from one place to another and the high percentage of mortality, 

 amounting in many farms to 100 per cent. 



SOME OBSERVATIONS ON THE BIOLOGY AND PATHOGENIC ACTIVITY 

 OF THE SWINE PLAGUE GERM FROM IOWA. 



In form this organism does not differ from the swine plague 

 bacteria obtained from various sources, East and West, since 1886. 

 In the tissues of rabbits, when these succumb within one or two days, 

 the germs appear as polar-stained bodies. In other words, when 

 stained in dried films on cover-glasses, the oval germs have both ex- 

 tremities deeply stained, while the central transverse portion or band 

 is nearly colorless. The reader is referred to the report for 1886 

 for further details concerning the form of this germ. In those 

 rabbits which do not die in so short a time, and in which the disease 

 develops into a peritonitis (when inoculation is practiced on the 

 thigh), the germs, although exceedingly abundant in the peritoneal 

 exudate, do not all show this polar stain. They resemble solid micro- 

 cocci more nearly. Their identity with the polar-stained forms is 

 easily settled by cultivation and inoculation into fresh animals. 



In cultures the germ is non-motile. It grows especially well in 

 beef peptone agar at 37 C. In bouillon, with or without peptone, 

 it grows very feebly, barely clouding the liquid. On the surface of 

 boiled potatoes no growth takes place as a rule, even when kept in 

 a moist atmosphere of 37 C. Only once was a faint development 

 observed with the naked eye. The growth was smooth, pure white, 



