494 THE POSTERIOR PITUITARY AND THE NERVOUS SYSTEM. 



rated by a fibrous lamina; and, furthermore, that "the poste- 

 rior lobe alone is connected with the infundibulum." . . . 

 "It is developed from the brain" and "is a dependence of the 

 middle ventricle." The anterior lobe is only connected with 

 the cerebral structures through vessels which, according to 

 Berkley, 8 "directly pass into it from the substance of the in- 

 fundibulum." The blood-supply of the posterior lobe is also 

 derived from the same source, but it is less rich, though suffi- 

 ciently so to satisfy the needs of an active function. Indeed, 

 the organs differ mainly in the character and wealth of their 

 nerve-supply much to the advantage of the posterior lobe, 

 however. The development of the anterior lobe from the 

 ectoderm of the primary oral cavity, instead of, as in the case 

 of the posterior lobe, from the embryonic brain, accounts for 

 what anatomical dissimilarities prevail. 



The histological characteristics of the posterior lobe also 

 suggest that it is the seat of some nervous function of a high 

 order. This is well illustrated by the exhaustive study by 

 H. J. Berkley 9 after an examination of some two thousand five 

 hundred slides. A summary of such a work hardly does it 

 justice; we must therefore refer the reader to the original 

 paper for details other than those that we will presently sub- 

 mit. 



The outer layer of the organ was found by Luschka and 

 Miiller to be composed of gray matter similar to that found 

 over the infundibulum. Berkley refers to this layer as com- 

 posed of slightly irregular ependymal cells three or four deep, 

 through which rather thick ball-tipped filaments penetrate to 

 the second anatomical subdivision of the lobe. This outer 

 coating of cells does not extend around the entire lobe, how- 

 ever, but covers only its free, or posterior, surface. Its ante- 

 rior portion, that nearest the partition between the two lobes, 

 has no such covering, so that its elements appear to be in con- 

 tact with the partition itself or to be only separated from it 

 by its capsule. The second subdivision of the posterior organ 

 occupies, judging from Berkley's drawings, about one-third of 

 its mass, and recalls, as to structure, that of the anterior lobe. 



Berkley: Brain, Winter, 1894. 

 Ibid. 



