192 SPECIAL HISTOLOGY. 



distended with fluid, without any fatty metamorphosis, and 

 presenting the same structure as in children. It is still more 

 difficult to assign the time of its complete disappearance, for 

 which no determinate age can be indicated, although it is 

 true that the thymus is usually not to be found after the 

 fortieth year. The disappearance takes place in consequence 

 of a gradual absorption, with a simultaneous development of 

 fat in the gland-granules and of fat-cells in the interlobular 

 connective tissue. At the same time, also, the concentric cor- 

 puscles multiply more and more and ultimately, according 

 to Ecker, even connective tissue is developed in the lobules, 

 the glandular structure being completely lost. 



[The investigation of the thymus is not easy. I recommend, 

 in the first place, boiled preparations, which of themselves are 

 very well adapted for the investigation of the connexion of the 

 lobes with the central canal, and the cavities in the lobules, 

 and when hardened in spirit are convenient for the making of 

 fine sections. Besides this, the hardening of recent prepara- 

 tions in alcohol, pyroligneous- and chromic acid, and the boiling 

 of them in acetic acid, are advisable. The thymus, also, of small 

 Mammalia, which is membranous at the edges, is well adapted 

 to afford a general knowledge. But moreover, and above all, 

 are injections of the human thymus indispensably requisite, 

 without which no satisfactory conclusions can be arrived at.] 



Literature. — S. C. Lucae, f Anat. Untersuchung d. Thymus 

 im Menschen und in Thieren/ Frankfurt am M. 181 1 u. 12, 

 4to, und ' Anat. Bemerk. uber die Divertikel am Darm. u. die 

 Hohlen des Thymus/ Nurnb. 1813, 4to; F. C. Haugsted, 

 ' Thymi in horn, et per ser. animal descrip./ Hafn., 1832, 8vo ; 

 A. Cooper, ' Anatomy of the Thymus Gland/ Lond., 1832, 

 4to ; J. Simon, ' A Physiological Essay on the Thymus Gland/ 

 Lond., 1845, 4to ; Ecker, Art. ' Blutgefassdrusen/ in Wagner's 

 « Handw. der Phys.' III. 



