No. I.] BLOOD CORPUSCLES. 85 



different kinds of cells was obtained, and observations made 

 upon different individuals were capable of a closer comparison. 

 It cannot be doubted that in its essential features, certainly, 

 and in all probability in most of the minor details, the genesis 

 of the blood corpuscles in the cat is the same as in man or in 

 any of the higher mammalia. 



In the course of the work I have made use of many different 

 methods of treatment ; but the methods which I have used 

 most, and which have given me the best results, are these. 

 When studying fresh specimens of liver blood, marrow, etc., 

 the reagent invariably used was a i per cent solution of 

 methyl green made up with 0.6 per cent solution of sodium 

 chloride. The tissue was teased either in normal salt solution 

 or in its own plasma, and then further teased in a drop of 

 the methyl green. I did not use acetic acid in combination 

 with the methyl green, as this reagent quickly dissolves out 

 the haemoglobin from the nucleated red corpuscles, while 

 with the methyl green alone this does not happen unless the 

 quanity used is too great relatively to the amount of tissue 

 teased. The blue-green color given by the methyl green to 

 the nucleus of the nucleated red corpuscles served to make 

 the haemoglobin in the cell protoplasm more distinct by con- 

 trast. The fresh tissue was examined also without the addition 

 of any staining reagent after teasing in its own liquid, in 

 normal salt solution, or, best of all, in blood serum which had 

 been previously prepared from the same animal. 



The marrow, spleen, and liver of the foetus as well as the 

 adult were studied in section, and specimens were taken from 

 normal animals, from animals which had been bled, starved, 

 injected, etc. 



The tissue was usually hardened in a cold saturated solution 

 of mercuric chloride according to the directions given by Gaule. 

 Sections were cut in paraffin, and were stuck to the cover slip 

 by the alcohol method, using 70 per cent alcohol. The sec- 

 tions were then stained by two or more different methods. 

 The stains usually employed were : first, a triple stain of 

 haematoxylin, eosin, and saffranin, used successively according 

 to Gaule's method ; second, alum carmine ; third, Biondi's 

 triple stain of acid fuchsin, methyl green, and orange used in 

 mixture ; fourth, the Shakespeare-Norris stain for haemoglobin, 



