244 VOL UTION AND DISEASE. 



usually attached to hairs, but may occur in situations 

 where hairs are not found normally. A number of tubu- 

 lar glands .may be collected together and give rise to a 

 compound organ like the kidney ; in the same way a 

 collection of racemose glands may form a compound 

 organ, such as the salivary glands, or the poison glands 

 of snakes. In complex animals like vertebrata, glands 

 of peculiar character are restricted to definite parts of 

 the body. Thus sebaceous glands are almost peculiar to 

 the skin ; mucous glands to mucous membrane, and so 

 forth. Thus it comes to pass that there are frontier lines, 

 and as a rule these lines are not violated. For instance, 

 at the lips the territory of sebaceous glands ends and 

 that of mucous glands commences. At the termination 

 of the large bowel or rectum, a similar condition of things 

 exists, Lieberkiihn's follicles so characteristic of the 

 bowels terminate. Numerous frontier lines of this nature 

 exist in our bodies. Another fact of considerable im- 

 portance is that at birth an animal is not furnished with 

 all the glands it will require, the germs of many arise 

 in after-life and even subsequent to the years of active 

 growth. In the chapter on supernumerary mammae, it 

 was pointed out that in recesses of skin or mucous mem- 

 brane glands grow luxuriously, and to this may be added, 

 especially if the recess is moist. 



In young individuals we find occasionally in connec- 

 tion with a functional gland, a tumour which when 

 examined microscopically displays all the features pecu- 

 liar to the gland with which it was connected ; the only 

 point in which it differs is that the adventitious mass is 

 impotent, that is, it cannot produce the secretion peculiar 



