284 PROCEEDINGS OF THE ACADEMY OF [^r^Xj 



ABSORPTION AND SECREnON IN THE DIGESTIVE SYSTEM OF 

 THE LAND ISOPODS.' 



BY JOHN RAYMOND MURLIN, PH.D. 



I. Introduction. 

 II. Material and raetliods. 



III. Description of the digestive system. 



1. Gross structure/ (I) The intestine ; (2) Glands. 



2. Microscopical structure, (1) Growth of the intestine ; 



(2) Origin of the typhlosole ; (3) Syncytium — i. Cyto- 

 plasm, b. Nucleus, (an) Form, (bb) Structure; (4) Moult- 

 ing — a. Changes in the cells incident to moulting. 



3. Summary of structure. 



IV. Feeding experiments, 1. Etlects of starvation. 



V. Absorption of proteids. Table I, giving changes in the cells ; 



Table II, precipitation of proteids. 

 VI. Function of the typhlosole. 



VII. Absorption of carbohydrates. 



VIII. Absorption of fats. 



IX. Secretion in the hepatopaucreas — a. Relation of secretion to feed- 

 ing. 

 X. Summary and conclusions. 



I. Introduction. 



While the teudeucy at this day is to approach physiological 

 problems chiefly from the experimental and the chemical standpoints, 

 there is yet need of many morphological observations to supplement 

 these more ultimate researches. The chemical history of the trans- 

 formation of foods into tissues has advanced considerably beyond 

 the morphological history, becau.se until recently no means has been 

 at hand for identifying them by morphological methods. Such 

 determinati(jn has been begun by Fischer (1)- in his studies on the 

 effects of flxing fluids on vari:nis proteid bodies and their deriva- 

 tives. 



Proteid foods have often been traced to the intestinal absorbing 

 cells, and have been identified in the blood of many animals after 

 having traversed the cells ; but their course in passing through the 

 intestinal epithelium and their relation to the various cell constitu- 

 ents have been little known. With the hope of throwing some 



' Contribution from the Zoological Laboratory of the University of 

 Pennsylvania. 



^Numerals in parenthesis refer to bibliographical list at the end of 

 the paper. 



