IJO BULLETIN OF THE BUREAU OF FISHERIES. 



ABSORPTION FAT IN THE TUNICA PROPRIA OF THE STOMACH. 



The tunica propria of the stomach is very complex in its convolutions because 

 of the fact that its net supports the irregularly shaped gastric glands. Varying quan- 

 tities of fat droplets are found in the tunica propria of the young salmon during the time 

 of absorption of fat. Often it happens that the connective tissue immediately beneath 

 the superficial epithelium is perfectly free of fat droplets, in fact, is always relatively 

 free of fat droplets. But during the active stage of absorption in the fat-fed specimens 

 occasional minute fat droplets are to be found, as shown in figure i , plate xii. In the later 

 stages the fat seems to accumulate in the tunica propria and is removed only after long 

 periods of time. In certain of the younger specimens observed the fat was still present 

 at a time at which the epithelial ceils were approximately free of fat droplets. In these 

 late absorption stages the tunica propria fat is chiefly limited to that portion which lies 

 just within the stratum compactum. The droplets are small in size and greater in 

 number between the bases of the deep gastric glands and the inner border of the stratum 

 compactum. 



It would seem that the connective tissue of the tunica propria, like that in the 

 intestine and pyloric coeca, holds on to its fat with great persistence. Stating the fact 

 in other words, the lipolytic process whereby the fat is removed from this region to 

 other parts of the body must proceed very, very slowly. It has seemed to the writer 

 that this connective tissue region serves as a temporary storage of absorption fat, also 

 that the process of dissociation and removal from the region is markedly influenced by 

 the presence of the stratum compactum. In the paper on the normal structure of the 

 alimentary tract emphasis was placed on the observation that the stratum compactum 

 is a continuous membrane. Only at points where it is punctured by blood vessels 

 entering into the deeper structures within the stratum is it punctured by other tissues. 

 This mechanical structural feature would throw upon the organs concerned the physio- 

 logical necessity of disposing of the fat by two possible channels. The first of these is 

 the vascular channel. In order that the fat may be taken up by the capillaries within 

 the tunica it must first be dissociated and diffused into the vascular channels. The 

 second possibility is that the fat may pass through the substance of the stratum com- 

 pactum. Here dissociation must also take place and be followed by diffusion through 

 the relatively thick and dense substance of the stratum. Since blood vessels of the 

 stomach do not form capillary nets in the statum granulosum immediately external to 

 the stratum compactum it follows that the fat diffusion must be carried through this 

 coat, i. e., the stratum granulosum, into the submucosa and muscular coats before it 

 could be taken up by the circulatory system and washed away into the general regions 

 of the body. In both instances the fat distributing process is comparatively slow, 

 hence one may expect the removal of the absorbed fat from the tunica propria to be 

 sharph? retarded. These points of view coincide with the facts of observation as 

 measured against the time which has elapsed from the moment of feeding and absorption 

 to the time of the preparation of the tissue for examination. 



