506 II. M. CARLETON 



employed (and in the same proportion to the volume of the 

 solvent) were made up in saline solutions of double the 

 normal concentration, i. e. of 1-8 per cent, and 1-2 per cent, for 

 the cat and frog respectively. 



The results for both cat and frog tissues may be summarized 

 as follows : 



6 per cent, mercuric chloride and 5 per cent, formol dissolved 

 in saline of double the normal concentration caused shrinkage 

 of the tissues examined. The degree of shrinkage was notably 

 greater in the formol than in the mercuric chloride series. 

 Further, while intestinal epithelium is relatively tolerant to 

 this increase in the tonicity of the NaCl, intestinal muscle and 

 liver are less so. Kidney showed both glomerular and tubule 

 shrinkage — especially in the formol series. The red blood- 

 corpuscles of the cat were crenated and distorted, while those 

 of the frog retained their normal shape. Finally, the mito- 

 chondria of the hepatic cells, after staining with iron haema- 

 toxylin, were found to remain unchanged no matter whether 

 the fixative (mercuric chloride or formol) were made up in 

 distilled water, isotonic saline, or hypertonic saline of double 

 the normal concentration. 



Conclusions. 



It appears to be of no histological importance whether 

 saturated (6 per cent.) solutions of mercuric chloride be dissolved 

 in normal saline or in distilled water. No differences could 

 be detected in specimens of liver, small intestine, and kidney 

 fixed in either way, nor would there be any reason to expect 

 such differences on a priori grounds. For the relatively 

 high molecular concentration of the HgClg is only very slightly 

 altered by dissolving it in either isotonic saline or in hypertonic 

 saline of double the normal concentration. In fact, the only 

 effect of making up a concentrated solution of mercuric chloride 

 in normal saline is slightly to increase the tonicity of the 

 mixture. 



In the case of a 5 per cent, solution of formol the evidence is 

 that . this reagent fixes tissues more faithfully when made 



