23 ANATOMY OF THE LYMPHATIC SYSTEM. 



tracts stands only in so far in a relation to the blood system as a 

 very active growth of capillary blood-vessels takes place in the 

 lymphangial nodules. We may say, further, that we consider fat 

 tissue, in agreement with Toldt, to be a special sort of glandular 

 tissue, for it develops from a special tissue, i.e. from lymphangial 

 nodules, which, as we have seen, have very much to do with the for- 

 mation of lymph-corpuscles, just as a lymphatic gland has. 



We have still to make a few remarks about the mesogastrium of 

 frogs. There are not seldom nodules to be found in the ground-sub- 

 stance, which are of a spherical shape, sometimes situated so closely to 

 each other that they almost coalesce, so as to form a cord, and which 

 are not always near the large blood-vessels. They have a structure 

 which resembles in all respects that of lymphatic follicles. 



As regards the mesentery, there is very little remaining to be said, 

 partly because we have already discussed the cellular elements of the 

 omentum, and partly because we shall return to the subject of the 

 cellular elements of the mesentery in the chapter on inflammation, 

 the cellular elements in the inflamed state being very much easier 

 to study than in the normal. This is especially true of frogs and 

 cats, in which animals chronic inflammation ocours accidentally, in 

 consequence of parasites which find their way from the intestine, 

 through the lymphatics of the mesentery, to the mesenteric glands. 



The cellular elements of the ground-substance of the mesentery 

 are in general more or less flat branched ; in their structure, size, and 

 nucleus they are not different from those in other serous membranes. 

 In frogs and monkeys, as well as in cats and dogs, I have not unfre- 

 quently seen, on pencilled silver preparations, places where the branched 

 cells of the lymph-canalicular system appeared to undergo division. 

 In some the nucleus is divided ; in others the body of the cells itself 

 exhibits a cross mark between the two nuclei, so that then the body 

 of the cell consists of two halves, touching each other in a straight 

 line. Sometimes a group of three or four of them were touching each 

 other in straight lines, either situated all round a common centre, or 

 arranged in a chain one after the other. In general, these phenomena 

 are seen to take place near the large blood-vessels. There, also, we 



