STUUCTUKE OF TIIYMUS. 



557 



Fig. 166 * 



head of a pin to a moderate-sized pea. Each lobule contains in 

 its interior a small cavity, or " secretory cell" and several of these 

 cells open into a small " pouch" which is situated at their base, and 

 leads to the central cavity, the " reservoir of the thymus" 



The Reservoir is lined in its interior by a vascular mucous mem- 

 brane, which is raised into ridges by a layer of 

 ligamentous bands situated beneath it. The 

 ligamentous bands proceed in various directions, 

 and encircle the open mouths- (pores) of the 

 secretory cells and pouches. This ligamentous 

 layer serves to keep the lobules together, and 

 prevent the .injurious distension of the cavity. 



When either gland is carefully unravelled by 

 removing the cellular capsule and vessels, and 

 dissecting away the reticulated cellular tissue, 

 which retains the lobules in contact, the reservoir, 

 from being folded in a serpentine manner upon 

 itself, admits of being drawn out into a length- 

 ened tubular cord,^ around which the lobules are 

 clustered in a spiral manner, and resemble knots 

 upon a cord, or a string of beads. 



The reservoir, pouches, and cells, contain a 

 white fluid "like chyle," or "like cream, but with 

 a small admixture of red globules." 



In an examination of the thymic fluid which I 

 lately made, with a Powell microscope magnify- 

 ing 500 times linear measure, I observed that 

 the corpuscles were very numerous, smaller than 

 the blood corpuscles, globular and oval in form, 

 irregular in outline, variable in size, and pro- 

 vided with a small central nucleus. 



In the human foetus this fluid has been found 

 by Sir Astley in too small proportion to be sub- 

 mitted to chemical analysis. But the thymic fluid of the foetal calf, 

 which exists in great abundance, gave the following analytical 

 results: one hundred parts of the fluid contained sixteen parts of 

 solid matter, which consisted of, 



Incipient fibrine, 

 Albumen, 



Mucus, and muco-extractive matter, 

 . Muriate and phosphate of potass, 

 Phosphate of soda, 

 Phosphoric acid, a trace. J 



* The course and termination of the " absorbent ducts" of the thymus of the calf; 

 from one of Sir Astley Cooper's preparations. 1. The two internal jugular veins. 2. 

 The superior vena cava. 3. The thoracic duct, dividing into two branches, which re- 

 unite previously to their termination in the root of the left jugular vein. 4. The two 

 thymic ducts ; that on the left side opens into the thoracic duct, and that on the right 

 into the root of the right jugular vein. 



t See the beautiful plates in Sir Astley Cooper's work. 



t This analysis was conducted by Dr. Dowler of Richmond. 



