54 LETTERS TO BROTHER JOHN. 



does not signify the thing separated. It is, how- 

 ever, sometimes better to retain an old word, 

 though a bad one, than run the risk of obscurity, 

 by introducing a new word. You are probably 

 aware that the word "gland" is derived from the 

 Latin word glans, which signifies an acorn : it was 

 given them from the supposed resemblance of some 

 of the glands to the appearance of acorns. 



There are several theories to account for the 

 manner in which a secreting gland is formed. The 

 most generally accepted, as well as the simplest, is 

 that of Ruysch. According to Ruysch, secretory 

 glands are formed by the convolution of minute 

 hairlike arteries, in the same manner as we have 

 just seen lymphatic glands formed by the convolu- 

 tion of lymphatic vessels : at a certain point of the 

 convolution, the blood contained in the arteries is 

 converted into the peculiar fluid which it is the 

 office of the gland to secrete ; at this point the 

 arteries lose the structure peculiar to arteries, and 

 assume that of excretory ducts. An excretory duct 

 is a small vessel, whose office it is to convey the new 

 secretion, from the point at which it is formed, to 

 the parts where its presence is required. But all 

 this will be made more clear by tracing some 

 particular artery, until it terminates in the for- 



