On Absorption. 169 



twenty-four hours As might have been expected, absorp- 

 tion and excretion were more rapid in the fowl than in- 

 the dog. 



It would be tedious to read the notes of all the experi- 

 ments, but any one wishing to do so, may at any time see 

 them. 



The following fluids and tissues of animals, frogs, birds, and 

 dogs, were microscopically examined when it was believed 

 that most dye was present in the body : 



Chyme, chyle. 



Fluid of mesenteric glands and lymphatics. 



Voluntary and involuntary muscular fibre. 



Muscular fibres and lining membrane of heart. 



Brain, spinal-cord, and nerves. 



Cartilage, bone. 



All epithelial structures. 



Liver, lung, spleen, and kidney. 



In none could I detect the slightest evidence of colour. 



We are then satisfied that although the dye permeates every 

 atom of the body, excluding only the densest tissues, its presence 

 cannot be discovered microscopically in any. Is it then 

 absorbed by the blood discs, or does it become an undistin- 

 guishable part of the serum ? 



Microscopical Examination of the Blood. 



Many difficulties lie in our way, some of which may be 

 considered insurmountable. 



1st. The evidence of colour is very untrustworthy, depend- 

 ing as it does upon the power of appreciation of the 

 observer, and it becomes much more so when the subject of 

 observation is a microscopic particle, something requiring a 

 quarter inch objective to discern and describe. It varies 

 also with the colour of the light transmitted, as we use a 

 white cloud, blue sky, or light from a lamp. 



2nd. Too much stress must not be laid on the very minute 

 quantity of colour necessarily present in any particle so small 

 as a blood corpuscle, for the dye is readily visible when really 

 absorbed, in particles very much smaller. 



3rd. By far the greatest difliculty lies in the diffracting 

 power of the red corpuscles, whereby the rays of light are 

 made to interfere, and this is especially the case when the 

 blood having been first dispersed with the point of a scalpel 

 over the slide, is allowed to dry. It constantly happens that 



