DISEASES OF THE OX AND SHEEP. 329 



If it is not always an easy matter to diagnose a disease in any 

 individual man or animal, owing to notable differences which 

 very frequently present themselves, it is doubly difficult to decide 

 whether or not there is sufficient justification in any particular 

 case for applying to a malady exhibited in one kind of animal the 

 same name as that which is used to denominate a disease in 

 another kind of animal. Of course there are not a few cases in 

 which we use the same appellation without any hesitation. For 

 instance, both in the matter of its origin and in that of its 

 characteristics, rabies is a disease which varies but little in 

 different animals. There are many instances, however, in which it 

 is a matter of no small debate how far the resemblances which 

 do exist justify the use of the same name; for though the 

 similarities may be great, the diseases may nevertheless be 

 altogether and essentially different. 



Though, then, we should in pathology, as in all other studies, 

 be on our guard against a tendency to remark dissimilarities 

 rather than resemblances, we must also avoid laying too much 

 stress on similarities found among things which are in reality 

 distinct. Such a mistake was made in the case of measles and 

 scarlet fever, and as a matter of fact down to about the middle 

 of the sixteenth century these two diseases as occurring in man- 

 kind were not considered to be different maladies. It was only 

 after closer inspection that their distinguishing characteristics 

 were remarked. Again, at the present time it is difficult to 

 decide how far swine fever is allied with typhoid fever of man, 

 though it is probable that the two are very intimately allied. 

 Further, if we turn to scarlet fever of man, and inquire if there 

 is any disease of the ox closely corresponding with it, we are 

 confronted with an arduous point of dispute. 



In the attempts we shall make to throw light upon this most 

 important point — important because it so intimately affects the 

 human race — we shall in the first place make a few observations 

 regarding this fever as it presents itself in man. We shall then 

 discuss briefly the characters of the bovine diseases known as 

 erythema mammillarum and as scarlatina respectively. In pass- 

 ing we may now remark that these are probably the same disease 

 as that which has recently been described by Power, Cameron, 

 and Klein, and at the same time that the former is possibly 

 simply a state occurring sometimes more and sometimes less 



