1902.] NATURAL SCIENCES OF PHILADELPHIA. 311 



au open structure ou the free margin of the cells, and, secondly, to 

 furnish some substance essential to the formation of the intima. 



IV. Feeding Experiments. 



We come now to the main purpose of this paper, namely : to con- 

 sider the cellular phenomena during the absorption of foods. We 

 shall take up in order the changes to be observed in the cell during 

 the process of absorbing (a) proteid and (6) fatty foods, reserving 

 for later consideration the changes effected ■within the lumen by the 

 digestive fluids under the subject of secretion in the hepatopancreas. 



It will be necessary to mention briefly the methods of feeding. 

 Animals were starved for various lengths of time, then allowed to 

 eat fresh raw beef for ten minutes, after which they were isolated 

 and killed at successive intervals. Table I (which appears at the 

 end of the paper) is arranged with reference to the number of hours 

 after feeding at which the intestines were fixed. Other foods con- 

 taining proteid, such as raw and cooked oatmeal, bread, white of 

 egg and other meats, were used for control and comparison, but by 

 far the larger number were fed finely-chopped raw beef. For uni- 

 formity only those which were fed on beef are mentioned in the 

 table. ^ 



(1) Effects of Starvation. 



In examining cells after feeding, two factors are to be carefully 

 separated, namely : the effect of previous starvation, and the change 

 produced by the food. It will be necessary now to make mention 



' Some precautions had to be taken to induce the animals to feed con- 

 tinously. Thus, if they were brought from a dark room directly to a 

 well-lighted one, none would eat unless protected from the light by an 

 opaciue object— a chip or bit of black paper. On the other hand, if kept 

 in the light for several days the animal became accustomed to the 

 greater intensity, and would usually eat at once. Even these would eat 

 more contentedly if the food were spread on the under side of an object, 

 as a box-lid, and this placed at an angle so that the animal's body was 

 suspended. Again, if thej^ were allowed to find the food in the course of 

 their wanderings, the chances of eating continuously were improved. 

 Even with these precautions the only way to be sure of the time was to 

 watch tiie individual and keep note 1)y some mark, such as a spot of 

 asphalt-cement or India-ink on the dorsum. Ten minutes continuous 

 eating was found to be a good average meal of beef. iMention has 

 already been made of the dilute condition in which the land isopod ob- 

 tains its food. If after long starvation one were allowetl to till the intes- 

 tine entirely full, the result was sometimes fatal ; although after a shorter 

 period of starvation or taken fresh from the natural state, they could be 

 kept alive indefinitely on a constant meat diet. 



