THE SPLEEN. 567 



organ observed 5 or G hours after the ingestion of food, noticed bj 

 many observers. In animals, besides these contractile elements, tiic 

 muscles of the coats and trahccida' which I have discovered, may take 

 some part in this process, and their presence further accounts for the 

 circumstance that the spleens of Animals contract bj galvanism, uhile 

 that of man does not [vid. Mikr. Anat. 11. 2, p. 265). 



§ 170. Physiological remarks. — The spleen is developed at the end 

 of the second month, in the ftictal mesogastrium, at the fundus of the 

 stomach, from a blastema which, derived from the middle layer of the 

 germ, independently of the stomach, the liver, or the pancreas, collects 

 in this situation. It is, at first, a whitish, often slightly lobed body 

 (0-72 of a line in length, 0-4 of a line in breadth, in the ninth to the 

 tenth week), which gradually becomes red and is very soon as rich in 

 blood and in vessels as in the adult. The roundish small cells, of which 

 the spleen is at first entirely constituted, become, in the third month, 

 partly developed into vessels and fibres, whilst another portion remains 

 as parenchyma cells. The Malpighian corpuscles are not formed till 

 subsequently, but may always be found at the end of the foetal period, 

 although considerably smaller than afterwards. I do not know how 

 they are formed, but I presume that they proceed from simple masses 

 of cells, whose external elements become metamorphosed into the coat 

 of connective tissue, whilst the internal ones, partly persisting in their 

 original condition, partly becoming metamorphosed into vessels, form the 

 contents. 



This is not the place to discuss at length ihe functions of the spleen ; 

 I must refer to my " Mikroskopische Anatomie," II. 2, p. 282, and 

 content myself here with stating, that I consider the spleen to be an 

 organ into whose parenchyma constituents of the blood enter bodily and 

 at times in increased quantity, and, with the co-operation of cellular 

 elements, which are in a state of continual formation and solution, un- 

 dergo, more especially a retrogressive, but partly also a progressive 

 metamorphosis, in the end to be taken up again by the blood and 

 lymphatics, in order to be excreted from the body or further applied to 

 the purposes of the organism. 



Up to a certain point the investigation of the spleen presents no dif- 

 ficulties ; the pulp, the trabecida', and the Malpighian corpuscles, are 

 at once obvious. The latter are most readily examined in the Pig and 

 Ox, where the coat and the contents may easily be isolated, and the 

 connection with the vessels is also apparent. To see blood-corpuscle- 

 holding cells, the addition of water must be avoided. The muscular 

 fibres are beautifully seen in the finer traheculce of the Ox, and in the 

 trabeculce of the Pig and Dog ; and here maceration in nitric acid, of 



