THE AMERICAN' 



MONTHLY 



MICROSCOPICAL JOURNAL. 



Vol. XV. APRIL, 1894. No. 4. 



On the Means of Distinguishing Human Blood. 



By henry L. TOLMAN, 

 chicago, ill. 



[Address before the Microscopical Section of the Chicago Academy of 

 Sciences, January 1:2, 1894]. 



Although the question of distinguishing human blood 

 from that of other animals may appear to be already de- 

 cided, yet it is by no means settled, and in fact the study 

 is yet in its infancy. There are so many factors involved, 

 so many nicely balanced questions to be considered, that 

 the subject is one of great difficulty. 3Iucli of the work 

 that has already been done must be done over again, all 

 of it must be carefully revised in the light of recent at- 

 tainments in technique and objectives. 



Let us then consider the subject theoretically and de- 

 cide what steps should be taken if the examination were 

 to be made for the first time. The blood is a fluid of 

 complex chemical composition ; is it not possible to find 

 some constituent in one kind, human blood, for example 

 which is not found in other kinds, that of the lower ani- 

 mals? We know that man eats different food from other 

 animals, that he lives differently, that he is protected by 

 clothes and sheltered in a home, that he is able by his 

 intellect to avoid dangers and in a measure to absolutely 

 neutralize the law of natural selection and survival of the 

 fittest. Now of course any long continued cause acting 

 on an organism, will necessarily modify it to a greater or 

 less extent, and it seenis natural that the human organ- 



