ISOTONIC SALINE AND DISTILLED WATER AS SOLVENTS 503 



eosin as a standard method, supplemented by Heidenhain's 

 iron-haematoxylin followed by Lichtgrun. 



(5) Finally, the question of personal bias (far more important 

 than is generally supposed) was dealt with in the following 

 manner : the identification numbers on the slides were covered 

 with unmarked labels. The degree of tissue-change was then 

 carefully noted for every slide in each series. Only then were 

 the labels taken off the slides. I am convinced that methods 

 such as these are necessary if minute differences in tissues 

 either in response to variations in the fixative or, indeed, to 

 any other factors, are to be accurately recorded. 



It is usually impossible to check histological observations 

 by quantitative methods. Only in certain specialized spheres, 

 e. g. the counting of cells in body and other fluids, can this be 

 done. It is therefore imperative in qualitative observations — 

 such as those forming the subject of this note— to adopt every 

 means whereby the conditions of experimentation can be 

 standardized, and the personal factor reduced to a minimum. 



The Comparative Effects of Using Normal 

 Saline and Distilled Water as Solvents for 

 Mercuric Chloride and Formol. 



Amphibian and mammalian tissues were used for these 

 observations. The following organs were studied : 



In the Frog . — Liver and small intestine. 



In the Cat.— Liver, duodenum, and kidney. 



Liver was chosen because the relatively large size of the 

 hepatic cells renders observation of their size and shape com- 

 paratively easy. The abundant blood in the sinusoids of this 

 organ also enables the behaviour of the red blood-corpuscles 



to be noted. 



Small Intestine was selected because it makes possible 

 the study of two different tissues— epithelium and non-striated 

 muscle — in the same section. 



Kidney was studied partly because of the histological 

 differences in the different portions of the urinary tubule, 

 partly on account of the sensitivity of renal tissue to the action 



