SCIENCE LETTER FROM PARIS. 206 



Dutch than other breeds of stock ; the cattle plague that decimates so many farms, 

 is communicated by cattle to each other from the slightest contact, while the closest 

 and most constant association is necessary to communicate the disease to sheep, 

 and even when they are affected, its action is not severe. Further, that plague 

 only attacks ruminant animals— oxen, goats, sheep, zebras, gazelles, etc. Ten 

 years ago this plague broke out in the Jardin d' Acchmatation ; not a ruminant es- 

 caped, and also one animal not of that class, a little tenant nearly related to the 

 pig — the peccat'i. 



Now, Dr. Condereau has demonstrated recently, that the stomach of the pig 

 has a rudimentary organization recahing that of the ruminants. Clearly the 

 stomach of the peccari, and perhaps that of the pig, present^a favorable medium 

 for the parasitical microbe peculiar to the rhinderpest. In the potato disease 

 again, all the varieties are not affected with the same degree of violence, it is 

 more marked in its action on the round yellows than the reds, and on the latter, 

 rather than the pink. But the symptoms even of the same malady differ, the par- 

 asite's attacks on the tissues being dissimilar. Oak galls are produced from the 

 prickings of insects; now around the same larva, often four varieties of galls are 

 recognized. In the case of consumption in cattle, the disease marches slowly; in 

 that of pigs it takes the galloping form, as with man. 



Each people or nation has its peculiar pathology and also its peculiar cures. 

 A negro can take a dose of tartar ten times more excessive than a white; the 

 same dose of brandy given to a black, a yellow and a white, will not produce on 

 the three men, either drunkenness at the same moment, or intoxication at all. 

 Mulattoes can sustain more drastic aperients than other races ; the negro does not 

 suffer from yellow fever, but he readily falls to phthisis ; he will catch the cholera 

 more quickly than a white. Human races where they may catch the same inter- 

 mittent fever at the identical moment and in the same swamp, will not the less dis- 

 play different types of fever. Dr. Crevaux has shown that a certain insect with 

 the North American Indian is not the same as with the negro or the maroon, and 

 both differ from that peculiar to Europeans. 



M. Pasteur's beautiful experiments have conclusively demonstrated that 

 fowls do not catch the charbon ; now the vital warmth of birds is from seven to 

 nine degrees higher than in the case of mammiferous animals ; he imagined that if 

 the fowl was cooled down by baths to the lower temperatnre, it would be liable 

 equally to become affected ; he tried, and the result proved he was correct. The 

 absence then, of a certain temperature would be the reason why birds are exempt. 

 The microbes are the agents of infectious disease : when these swarm in the 

 blood of an individual, they seem to leave there something pernicious for parasites 

 resembling themselves, or to bring away with them something necessary to the 

 hfe of their successors. A glass of sugar and water where leaven has already fer- 

 mented and yielded alcohol, is incapable of producing a second crop of leaven ; 

 similarly the blood of an individual once contaminated, becomes uninhabitable 

 afterward for like microbes. The individual has acquired immunity. Such is 

 the principle of vaccination, 



