CONTAGIOUS DISEASES OF DOMESTICATED ANIMALS. 137 



until they have become harmless, and harmless germs, until they have 

 become pathogenic. 



Under prophylaxis Degive adduces instances in which a thorough at- 

 tention to the laws of hygiene in ventilation, lighting, feeding, &c., have 

 seemed to arrest the propagation of the poison. In this as in the ques- 

 tion of spontaneity the experience of Degive, limited to a country in 

 which the disease constantly prevails, is misleading. He fails to take 

 into account such sweeping evidence as the entire absence of the lung- 

 plague from America, South Africa, and Australasia until the occur- 

 rence of a single importation of disease, and its deadly prevalence in 

 all ihree froui that moment onward, notwithstanding that in the two last- 

 named places the victims enjoyed an open-air life in mild and equa- 

 ble climate, the most favorable possible for the lungs. He further ig- 

 nores for the instant the irregular and occult cases of the disease which 

 confer immunity, and at once explains the sudden disappearance of the 

 disease in i)articular herds coincidently with a better hygiene or a worse 

 one, and the introduction of infection into a new locality where the best 

 eflbrts of the veterinarians have failed to trace its source. 



Degive strongly advocates inoculation, supporting his view by the 

 following facts : 



1. Oat of 6,700 inoculated cattle placed in the same pathogenic con- 

 ditions as 2,453 non-inoculated ones, 182 only, or about 2.71 per cent, 

 among the first, and 660, or 26.90 per cent, among the second have con- 

 tracted lung plague. 



2. Out of 68 previously inoculated in the tail or by intravenous in- 

 jection, and in which a second inoculation was practiced in a region 

 rich in connective tissue (a deadly region), 61 have shown no local re- 

 action, and 5 j)resented a slight intlammatory swelling, which in 6 beasts 

 inoculated for the first time in the same dangerous regions, as test cases, 

 all had an extensive iutiaininatory engorgement ending in death. Oat 

 of 6 animals inoculated b^' intravenous injection in the jugular and 

 afterward subjected to 17 inoculations in the space of 16 mouths, 4 

 proved unaffected, 13 had slight inflammatory reaction, and 1 only had a 

 considerable engorgement which did not jirove fatal. 



The immunity secured by inoculation has lasted four and five 

 years, as observed by Ziegenbeiu, in animals constantly exposed to in- 

 fection, and for one year in 16 test cases in the experiments of the 

 Central Society of Veterinary Medicine of Paris. 



The drawbacks to the operation are : 



1. All the inoculated do not acquire a perfect immunity. 



2. Inoculation preserves and spreads the poison. 



3. A certain small proportion die from the extensive swellings and 

 gangrene conseciuent on the inoculation. 



That all the inoculated are not protected is shown in the above sta- 

 tistics ; some highly susceptible animals still contract the disease as 

 some men contract small-pox after vaccination. To secure a better im- 



