THYMUS GLAND. 



Fig. 246.* 



557 



Fig. 247.f 



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 pre- 

 vent the injurious distension of the cavity. 



When either gland is carefully unravelled by re- 

 moving the areolar capsule and vessels, and dissecting 

 away the reticulated areolar 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 lengthened 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 (1840) made, with 

 a Powell microscope magnifying 600 times linear measure, I observed 

 that the corpuscles were very numerous, smaller than the blood particles, 

 globular and oval in form, irregular in outline, variable in size, and pro- 

 vided with '* small central nucleus. 



In the human foetus this fluid has been found by Sir Astley Cooper in 

 too small proportion to be submitted to chemical analysis. But the thy- 

 mic fluid of the fcetal calf, which exists in great abundance, gave the fol- 



* A section of the thymus gland at the eighth month, showing its anatomy. This 

 figure, and the succeeding, were drawn from two of Sir Astley Cooper's beautiful pre- 

 parations, with the kind permission of their possessor. The references were made by 

 Sir Astley's own hand. 1. The cervical portions of the gland ; the independence of the 

 two lateral glands is well marked. 2. Secretory cells seen on the cut surface of the 

 section ; these are observed in all parts of the section. 3, 3. The pores or openings of ; 

 the secretory cells and pouches; they are seen dispersed upon the whole internal sur- 

 face of the great central cavity or reservoir. The continuity of the reservoir in :he 

 lower or thoracic portion of the gland, with the cervical portion, is seen in the figure. 



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. 



$ See the beautiful plates in Sir Astley Cooper's work. 



47* 



