1910.] NATURAL SCIENCES OF PHILADELPHIA. 5 



of the fluids from the muscularis toward the epithelium resulted in 

 the latter being torn loose from the underlying connective tissue. 

 At least this phenomenon was not infrequently manifesl and is 

 presumably to be credited to the direction of entrance of the fluids. 



Following fixation, each intestine was cut into piece- of a con- 

 venient length for embedding in paraffin. In general, the small 

 intestine was cut into 25 to 30 pieces which were numbered, as a 

 rule, from the anterior to the posterior end. Thus, int. 1 of a given 

 mouse indicated the piece immediately following the stomach, the 

 highest or last number that piece immediately in front of the csecum. 

 Sometimes, however, this process was reversed, the last piece of the 

 intestine being designated as int. — 1; the next to the last, int. — 2, 

 and so on, the negative sign's serving to distinguish such cases from 

 the more usual procedure. This, as already noted, is applicable to 

 the small intestine alone, the caecum and large intestine being given 

 other designations. The procedure as outlined above was not, 

 however, always followed. 



The fixing fluids used were: 



1. Hermann's fluid, stronger formula. 



2. Zenker's fluid. 



3. Picro-acetic acid, made by reducing a saturated aqueous 

 solution of picric acid to one-half strength with water, and adding 

 1 per cent, glacial acetic acid. 



4. An alcoholic-corrosive-acetic mixture, designated in the text 

 as A. C. A. The formula for this is as follows: 



Saturated aqueous solution of mercuric chloride 50 parts. 



Alcohol, 95 percent 50 parts. 



Glacial acetic acid '5 parts. 



Of these, Hermann's fluid and the picro-acetic mixture, the latter 

 despite Lee's strictures, gave the most delicate fixation. Zenker's 

 fluid is not to be recommended, since it leaves the tissues in poor 

 condition for staining and is at best a mediocre fixative. 



The A. C. A. fluid, while scarcely so accurate as Hermann's fluid, 

 is none the less a very good fixative. It is, moreover, very con- 

 venient, since the tissues can be passed directly from it into alcohol, 

 and it leaves the material in excellent condition for staining. 



The material was stained both in bulk and on the slide. While 

 t here is a prejudice against the former method for delicate cytological 

 work. Delafield's hematoxylin counterstained on the slide with 

 alcoholic eosin or acid fuchsin dissolved in 95 per cent, alcohol, gives 



