BUREAU OF ANIMAL INDUSTRY. 145 



careful study of this subject was made. After practical laboratory 

 experiments, together with tests of supposed cultures on pigs, the 

 conclusion was reached that the claims were not established, it be- 

 ing impossible to affirm from a microscopic observation that any 

 organisms had grown, and likeAvise impossible to produce the dis- 

 ease with the cultures when care w^as taken to make a sufficient num- 

 ber of subcultures to avoid any possibility of producing disease with 

 the virus with which the cultures Avere started. 



Additional data were gathered concerning the minimum fatal dose 

 of the blood of pigs sick of cholera. Defibrinated virus blood was 

 diluted with water or salt solution and injected subcutaneously into 

 susceptible pigs in amounts equivalent to one one-thousandth, one 

 three-thousandth, and one five-thousandth of a cubic centimeter of 

 the blood. xVll the pigs contracted hog cholera. It is probable that 

 the minimum fatal dose of blood from a pig suffering from acute hr)g 

 cholera is considerably less than one five-thousandth of a cubic centi- 

 meter. 



A few experiments were undertaken to compare the virulence of 

 hog-cholera defibrinated blood prepared with one-half per cent 

 phenol with that of clear virus and a filtered virus preserved in the 

 same manner and obtained from the same blood. The samples were 

 kept at room temperature ranging from 50 to 60° F. Pigs were in- 

 jected at the end of 30 days and 60 days after the preparation of 

 these different kinds of virus. All the injected pigs contracted hog 

 cholera. A number of the pigs were inoculated with hog-cholera 

 serum, some receiving at the same time the defibrinated blood virus, 

 others the filtered virus, and still others the ordinary clear virus not 

 filtered. These pigs are being held in order to determine whether a; 

 lasting immunity is conferred by these different injections. 



The study of diseases of hogs which are related to and which may 

 be confused with cholera has been continued. There are two different 

 affections of pigs in the Middle West, and perhaps in other parts of 

 the country, that may be mistaken for hog cholera and are of eco- 

 nomic importance. One is commonly called necrotic enteritis, so 

 called on account of the severe inflammatory condition observed in 

 the intestines of the affected pigs. Pigs affected Avith this disease 

 were procured and efforts were made to transmit it to others. In two 

 instances it was possible to transmit this disease to healthy pigs by 

 association and by feeding viscera of affected pigs. It was found, 

 however, that in order to communicate the disease by association it 

 was necessary to allow the pen to become very filthy. It appears 

 that this disease, to a considerable extent at least, arises from bad 

 sanitation and filth. When infected pigs were removed from the 

 insanitary conditions under which they had been kept and placed in 

 clean quarters and given proper food, as a general rule they made 

 progress toward recovery. 



The second disease, which is met with even more commonly than 

 necrotic enteritis, is the so-called "flu" of hogs. This condition ap- 

 pears as a herd disease. A large number of the pigs appear to be 

 extremely sick within a very short time and there is marked evidence 

 of pulmonary involvement. As a rule the disease runs a rapid course 

 and the most of the herd soon return to normal. The death rate is 

 low, probably not more than 2 per cent. Efforts were made to 



