IDENTITY IN DISEASES. 
141 
German entitled “ Histology of the Mammary Gland of the 
Cow, etc.,” to which the translator attached the following foot¬ 
note : a Perlsucht is the German name for the disease commonly 
termed tuberculosis , but it is doubtful if the name is applicable , 
etcP To which the editor of the Journal adds the following: “ In 
veterinary sanitary science and police , the question as to 
whether the tuberculosis or perlsucht of cattle is identical 'with 
tuberculosis of man has been fully discussed , and the views of 
Schuppel adduced in favor of this identity 
There exists at present among many veterinary writers, who 
are much better acquainted with literature than with questions 
belonging to pathology or Eetiology, a most intense desire to 
discover identities between the diseases of the domestic animals 
and man ; so far as the desire extends to a better knowledge of 
the cause of diseases, we also plead guilty, but our desire does 
not go beyond such cases as are capable of proof by direct exper¬ 
iment. Such identity is not to be established with a book of 
human pathology in one hand, a comfortable easy-chair and good 
cigar at command, with the waves of smoke circling round one's 
head, and dreamy reflections of possible identities occupying one’s 
brain; the work by which identities are established is much more 
severe. In reference to identity in diseases, these gentlemen 
all have the wrong end of rope in hand. They all seek the identity 
in the product and not in the (Etiological moment. Like causes 
do not invariably produce like effects in pathology, if they do in 
other things, not even by organisms belonging to the same species. 
Two persons are exposed to the same degree of cold. The one, 
on account of his intogenetic peculiarities, becomes a pneumonia 
and dies; the other, being of a tougher nature, becomes a catarrh 
of the naso-pharyngeal mucosas and recovers. It always takes 
two causes to determine a pathological effect. If these two are 
exactly alike in different individuals, the result may be (?) more 
likely to be the same ; a causa externa equals causa suficiens. 
In the case in question, we find writers assuming that the tuber¬ 
culosis of cattle and man must be identical, because the tubercle 
is the result , the product. We are perfectly aware that not only 
Schuppel bnt others pronounce the tubercles in both cases to be 
