OF THE THYMUS GLAND. 257 



capsule to the gland, and gives it a pretty regular smooth ex- 

 ternal surface, except where it is fissured into larger lobes. 

 But this capsule is not of that kind we find on some other 

 glands, as on the kidneys, &c., which can be readily separated 

 from them. It is nothing more than a coarser condensed re- 

 ticular substance adhering firmly to all parts of it ; from which 

 it cannot be separated, without doing injury to the glandular 

 substance (cxxiv). 



SECT. 27. Many attempts have been made, by dissection 

 and other means, to discover an excretory duct from this part. 

 For the organization being apparently the same in it as in some 

 other known glands, it was but natural to conclude that, similar 

 to them, it also should have an outlet. Accordingly, many 

 fruitless experiments have been made, and much time employed 

 to discover it, but with so little success, that all attempts of 

 that kind seem long since to have been given up. Nay, some 

 have been led into very unphilosophical conjectures, viz. that 

 perhaps it was useless, or that if it did perform any office, it 

 was so obscurely as to escape investigation. 



SECT. 28. But the ingenious author, whose experiments we 

 are about to relate, entertained too exalted an idea of Nature 

 to suppose that any part of the animal frame was useless, though 

 the structure of some parts might be so intricate, and their 

 uses so obscure, as to elude the researches of the most assiduous 

 and ingenious inquirers into the operations of nature. 



SECT. 29. Mr. Hewson, after having made many attempts 

 by dissection and injections to discover the use of this gland, 

 with almost as little success as his predecessors, began to employ 

 the microscope ; but microscopical experiments, in the manner 

 they were then conducted, afforded no other satisfaction here 

 than that the blood-vessels were distributed in a similar manner 

 to those of the lymphatic glands ; but the external appearance, 

 as well as the minute structure of the thymus (so exactly cor- 



(cxxiv.) The structure of the thymus has been particularly described 

 by Sir Astley Cooper, a Dr. Haugsted, b and Mr. Simon. c The two 

 authors last named have given full notices of the labours of the earlier 

 writers on the subject. 



a Anatomy of the Thymus Gland, 4to, logica, et Physiologica. 8vo, Hafniae, 



Lond. 1832. 1832. 



b Thymi in homine ac per Seriem Ani- f A Physiological Essay on the Thymus 



malium descriptio Anatoiuica, Patho- Gland, 4to, Lond. 1845. 



17 



