1902.] NATURAL SCIENCES OF PHILADELPHIA. 289 



k, Flemming' s ; I, Hermann's, and m, Hermann's without acetic 

 (one per cent, platinic-chloride 15 parts, one per cent, osmic acid 4 

 parts). For minute cytological details I liave relied most on a, 1% 

 I, m, because these are most faithful to the structure in fresh cells. 

 Further consideration of the effects of fixation on the different cell 

 constituents and the metabolic contents will be taken up under the 

 appropriate heads. 



For studying the structure in fresh cells, the organs were mounted 

 in the blood of other animals of the same species, as follows : Upon 

 a slide a small rectangular fragment of cover-slip was supported by 

 a fragment of glass of suitable thickness, the other end resting on 

 the slide. The blood was now squeezed out of a decapitated ani- 

 mal in the form of a large drop, which, applied to the edge of the 

 cover-glass, was drawn under by capillarity. From one to two 

 dozen animals, according to the size, are required to furnish suffi- 

 cient blood for a single intestine. The medium having been thus 

 prepared, the organs were drawn out of the animal, placed on the 

 slide, and arranged near the supporting glass parallel to the junction 

 of the two fragments. The quantity of blood was then noted by 

 a mark indicating its level on the cover-glass, and this level was 

 maintained by adding distilled water as water was lost by evapora- 

 tion. The chemical changes accompanying coagulation of the blood 

 do not seem to affect the cells at all within the first half -hour. 

 Post-mortem changes, however, do occur after an hour or two. 

 Consequently no structure as seen by this method has been trusted 

 beyond thirty minutes from the time of preparation. 



Most of my observations have been made on serial sections pre- 

 pared in the usual manner. Both " liver " and intestine were sec- 

 tioned, stained and mounted on the same slide. The stains upon 

 which most reliance has been placed are iron-hsematoxylin, Biondi- 

 Heidenhaiu, Flemming's triple, Hermann's triple and Altmann's 

 acid-fuchsine-picric-alcohol. The effects of these on the various 

 parts will be mentioned from time to time. 



III. Description of the Digestive System. 

 1. Gross Structure. 



It will be necessary to recall the gross structure of the digestive 

 system, as this can be made out with the luiked eye or a dissecting 

 microscope. 



1. The intestine takes the most direct course possible from the 

 mouth to the anus. Three chief divisions are generally recog- 

 nized : the anterior, consisting of the (esophagus and grinding 

 stomach {kaumagen, poche malaxatrice) ; the middle (" mid-gut," 

 intestine moyen'), in which three divisions will be recognized, and 

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