SECT. 170.] DEVELOPMENT OF THE SPLEEN. 373 



laries, while in another part the union occurs only through the pulp-spaces ; or 

 z, the hypothesis that the capillaries have generally no direct connexion with 

 the veins, but pass freely into the pulp; so that the splenic blood travels 

 ■without definite course through the pulp, just as by the latest observations, 

 the chyle travels through the alveoli of the lymphatic glands. From the 

 absence of conclusive evidence as to the facts, the choice between these two 

 hypotheses is difficult ; either of them is as available for the physiologist and 

 pathologist as the statements of Hlasek. In fine, I would maintain the 

 opinion I have already expressed as to the connexions of the vessels, for two 

 chief reasons: first, that in man the capillaries may be actually traced into 

 veins (in the Malpighian bodies, at all events) ; and secondly, that on no other 

 hypothesis can we understand the different reaction of the splenic pulp from 

 that of the blood in the vessels. 



This, then, being our conception of the circulation in the spleen, we are 

 certainly reminded somewhat of the corpora cavernosa in the larger mam- 

 malia, in which a part of the arteries and veins are connected by means of 

 at venous spaces, while in the thick trabecular capillaries are met with in 

 the ordinary manner. Suppose these spaces to be filled with a special paren- 

 chyma of cells, with capillaries running through it, and the structure would 

 present a considerable similarity to that of the spleen. In any case, however, 

 the pulp must not be regarded as merely a slowly moving blood rich in cells, 

 but as a more stable element, which, while it gives and takes materials from 

 the blood, still serves other purposes, as is indicated by the peculiar chemical 

 properties of the splenic juice and by its acid reaction. 



In the great obscurity which still surrounds the relation of the spleen pulp 

 to the blood-vessels, we may be allowed to give consideration to statements 

 which do not at first recommend themselves by being very intelligible. Such 

 are the views of Sasse, Billroth, and Gray. According to Sasse, the pulp-cells 

 are contained in tubes formed of homogeneous membrane with nuclei ; and, 

 1 ry the rupture of these tubes, the cells become free and metamorphosed. 

 Billroth states the parenchyma of the spleen to be a fine hollow network 

 made up of cells, into which the arteries finally open, and from whence the 

 veins spring; he comes to no conclusion about the formation of the red 

 blood-discs, though he thinks the process goes on in the cells of his network. 

 Gray, lastly, gives three ways in which the veins commence: 1. in direct 

 prolongation from the capillaries, the most usual way ; 2. from intercellular 

 spaces in the pulp ; and 3. by forming an imperfect envelope around the 

 Malpighian bodies. Through the vagueness of the two latter statements, 

 this author fails to afford a direct addition to our knowledge of the relations 

 of the vessels. 



§ 170. Plirjsiological Remarks. — The spleen begins its develop- 

 nt in the foetus at the end of the second month, in a fold of 

 peritoneum at the fundus of the stomach ; it originates from a 

 blastema, which has no connexion vi ith the stomach, liver, or 

 pancreas. At first it is a whitish body, often slightly marked into 

 lobes, and assumes a red colour, from the development of blood 

 and vessels within it. The roundish cells, which at first compose 



