522 



THYMUS. 



[CHAP. xxxv. 



Fig. 251. 



of the gland contains granular matter, with numerous nuclei 

 dispersed through it. In a thin section, the outline of the cavities 

 can be readily seen ; they vary from the l-50th to the 1-1 8th of 

 an inch in diameter, and contain numerous granular and nearly 

 spherical nuclei, which are, for the most part, about 1 -4000th of 

 an inch in diameter, but vary considerably in* size. Dr. Handfield 

 Jones observes, that before any appearance of atrophy has taken 

 place, these elements are alone found, and there is an entire ab- 

 sence of oil particles, and granular 

 material. The nuclei seem to fill the 

 ultimate vesicles completely. 



Uses of the Thymus. Mr. Simon 

 regards the secretion of the thymus 

 as allied to proteine, and of a nutri- 

 tious nature. 



In the human foetus, the thymus 

 cannot be detected before the ninth 

 week, and its functional activity is 

 greatest in the early period of life, 

 before the muscular system is in a 

 very active state; for when the 

 muscles become more fullv active, 



a. Binary and quai ternary division of sim- 

 ple follicles. 6. Unusual appearance in ^he thvHlUS appears liot to be re- 

 \vhich the follicles must have increased con- * 



siderably in length before undergoing divi- quired. It Seems Connected With 

 sion. From the foetal lamb. 



c. Mature structure of thymus, showing the th e preparation of matter for the 



arrangement of the vesicles belonging to one L r , 



cone. d. Tube of giand. After Simon, pulmonary organs in the age ot 



early growth." Arguing from these 



and many other facts, Mr. Simon looks upon the thymus as acting 

 " as a sinking fund in the service of respiration." From 

 twentieth to the twenty -fifth year it diminishes rapidly in sis 

 until no trace of it can be detected in the areolar tissue of tl 

 mediastinum. In hybernating animals, previous to the comment 

 ment of the winter sleep, the thymus becomes gorged with fat, 

 which is slowly consumed during the period of hybernation. It 

 has been remarked, that the use of the thymus at the different 

 periods of active growth and hybernation is distinct. In the latter 

 case, it doubtless supplies hydro-carbonaceous matter for respira- 

 tion; but its office, during the former period, appears rather to be 

 that of elaborating fibrine from albumen and other substances by 

 the action of its numerous nuclei. As the absorbent and other 

 glands connected with the vascular system become developed, 

 there seems no longer any need of a special organ for this pur- 



