THYMUS GLAND 387 



perature of 105 Fahr. (40.5 C.) after the general symptoms made their 

 appearance, they could be kept alive for several months. Recent 

 experiments on animals (Lanz) and observations on the human subject 

 (Halsted) seem to show that the thyroid has some relation to the 

 generative function, its absence or disease greatly impairing fecundity 

 and sexual activity. 



It is difficult to draw from these various observations absolutely 

 definite conclusions in regard to the physiological relations of the 

 thyroid. This organ seems essential to life and its removal profoundly 

 affects the general processes of nutrition. It influences the quantity of 

 mucin in the body, but precisely in what way it is difficult to determine. 



THYMUS GLAND 



In its anatomy the thymus resembles the ductless glands, but its office, 

 whatever this may be, is confined to early life. In the adult the organ 

 is wanting, traces, only, of fibrous tissue, with a little fat, existing after 

 puberty, in the situation previously occupied by the gland. As there 

 never has been a plausible theory, even, of the uses of this organ, the 

 existence of which is confined to the first two or three years of life, it 

 seems necessary to give only a brief sketch of its structure. 



The thymus appears at about the third month of foetal life and grad- 

 ually increases in size until near the end of the second year. It then 

 undergoes atrophy and disappears almost entirely at the age of puberty. 

 It is situated partly in the thorax and partly in the neck. The thoracic 

 portion is in the anterior mediastinum, resting on the pericardium and 

 extending as low as the fourth costal cartilage. The cervical portion 

 extends upward as far as the lower border of the thyroid. The whole 

 gland is about two inches (50.8 millimeters) in length, an inch and a 

 half (38 millimeters) broad at its lower portion, and about one-quarter 

 of an inch (6.4 millimeters) thick. Its color is grayish with a slightly 

 rosy tint. It usually is in the form of two lateral lobes lying in apposi- 

 tion in the median line, although sometimes there exists but a single 

 lobe. It is composed of a number of lobules held together by connec- 

 tive tissue. 



The proper coat of the thymus is a delicate fibrous membrane sending 

 processes into the interior of the organ. Its fibrous structure, however, 

 is loose, so that the lobules can be separated with little difficulty. Por- 

 tions of the gland may be, as it were, unravelled, by loosening the 

 interstitial fibrous tissue ; and in this way it is found to be composed 

 of little lobular masses attached to a continuous cord. This arrange- 

 ment is more distinct in the inferior animals of large size than in man. 



