The discovery of the nature of the spleen : from an investigation of the lateral homologies of the liver, stomach, and intestinal canal / by Henry R. Silvester.

  • Silvester, Henry R. (Henry Robert), 1829-1908.
Date:
1870
Catalogue details

Licence: Public Domain Mark

Credit: The discovery of the nature of the spleen : from an investigation of the lateral homologies of the liver, stomach, and intestinal canal / by Henry R. Silvester. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    that its anterior aspect is the left lateral homologue of the posterior. Passing now from the regions of specu- lation, the intestinal canal can be witnessed in tlie em- bryo as a straight, uniform, mesial, and symmetrical tube, uutil its length, having become greater than that of the region which it is destined to occupy, it is com- pelled to arrange itself in gyrations and loops. The pos- terior and anterior walls of the stomach were originally, as indicated above, its right and left halves, and as to the other parts of the alimentary tube, whatever difficulty there is in recognizing the manner of their displacement in the human subject, is at once dispelled by examining their condition in the lower animals. No difficulty what- ever is encountered in respect of the small intestine, for the mesentery is attached nearly in the median line. The bowels themselves, however, are continually varying their position, relative and positive, according to the manner of packing most convenient for their variable contents. Not so easy is it to understand the kind of displacement which has taken place in respect of the large intestine. The colon is cui-led back and crosses over the small intestine fi'om right to left, forming a loop. In the human subject the true relation of these parts is further marked by the singular circumstance of this crossing over occurring just at the point where the meso-gastrium, after having de- scended as the gi'eat omental bag is returning to the spine, and the colon finding it there, so to speak, avails itself of it and uses it as a mesentery. Anatomists have named the borrowed portion of the meso-gastrium, the transverse meso colon. In Ruminants, the colon being exceedingly long, avails itself also of the mesentery of the small in- testine into which a loop of it is thrust further and further, until it makes three turns, so that in tracing the colon onwards with the finger, you make the spiral turns in the mesentery, and then double and return by the spiral tiu-ns placed between the former spirals. On the other hand, in the (Jarnivora, where the colon is very short, it crosses over the lower end of the ileum, so near its termination, that it is evident that the next degree of shortening must result in the continuation of the small and large intestine in a straight line. This actually takes place in the Reptilia, and then there is no longer any