134 THE DISEASES AND DISORDERS OF THE OX. 



example of which anthrax may here be mentioned, nre connected 

 apparently by way of causation, with the presence of organisms 

 of microscopic size in the blood, the lymphatics, and in the 

 different parts of the tissues and organs. No doubt there are 

 certain conditions of receptivity on the part of the human beings 

 or the animals liable to be attacked by these germs, and although 

 at present we know very little indeed definitely on this point, 

 yet the information gathered in regard to these and allied ques- 

 tions, is gradually but surely growing, and already much has 

 been learnt respecting the best methods of coping successfully 

 with these living germs. Moreover, long and instructive as is 

 the list of those diseases which have been shown to be dependent 

 upon the entry of living germs into the blood, or upon the in- 

 roads made by them upon other fluids or structures of animals, 

 we may safely infer that the continuance of searching investiga- 

 tion will lead to similar conclusions regarding the causation of 

 other diseases not yet thus explained which affect human beings 

 or lower animals or both. Further, it is important to note that 

 while many of the maladies known to depend upon the presence 

 of living vegetable organisms in the fluids or tissues, or both, are 

 liable to afflict human beings, some are peculiar to lower animals, 

 whereas others are alike capable of attacking both human beings 

 and animals indiscriminately. In short, the relation betwixt the 

 diseases of human beings on the one hand, and those which 

 afflict animals on the other, is a close one, and one of the greatest 

 significance. The diseases, and especially those of a contagious 

 and infectious nature, such, for instance, as bovine scarlet fever, 

 from which Mr. Power and Dr. Klein have shown that in all pro- 

 bability human scarlet fever is capable of being derived, are now 

 attracting a very considerable amount of attention on the part of 

 bacteriologists and comparative pathologists which cannot fail 

 to affect very deeply all our ideas in regard to the various work- 

 ings of disease. Of the numerous diseases which afflict human 

 beings, some at least are liable to be communicated from lower 

 animals, and consequently our knowledge, in order to be com- 

 plete, must be supplemented by such information as can be 

 derived from studying the origin of these particular maladies. 

 The three dread diseases, known respectively under the names 

 tuberculosis, anthrax, and rabies, seem to primarily attack lower 

 animals, although they are also grave scourges to human beings, 



