DISEASES OF HAIR-SACS AND SEBACEOUS GLANDS. 387 



on the other by a painless suppurative disorganisation of the 

 joints which finally results in complete separation. 



§ 326. Glanders, communicated from the horse to man, 

 manifests itself also by the production of nodular deposits in the 

 subcutaneous areolar tissue. The deposits are entirely made up 

 of embryonic tissue, and differ from the corresponding products 

 of syphilis and leprosy in a speedier rate of change, terminating 

 invariably in suppuration. 



o. Diseases of the Hair-Pollicles and Sebaceous 



Glands. 



a. Retention of Secretions. 



§ 327. The hair-sac, with its appended sebaceous follicles, is 

 one of the most ingenious anatomical contrivances in the body. 

 The whole arrangement for the implantation of the hair into the 

 skin, the ingenuity with which it is provided for in the interior 

 of the hair-sac — all this agrees wonderfully with our notions of 

 the adaptation of means to ends. But, as in the case of many 

 an ingenious contrivance due to human skill, the advantages are 

 not without corresponding drawbacks. Both are easily put out of 

 order. The way in which the growing hair moves upwards along 

 its sheath, at whose narrowest part it is brought in contact with 

 the openings of the sebaceous glands, which oil it with their 

 secretion, and protect it against the adverse influences with 

 which it will have to contend upon its liberation — all this looks 

 wonderfully cunning and practical. But the very closeness of 

 this contact between the hair and the neck of the follicle has its 

 dangers. It wants but little to stop up the mouth of the follicle 

 completely. A trifling swelling of the subepidcrmic connective 

 tissue, a slight increase in the number of epidermic cells pro- 

 duced, is quite enough to fill the small amount of vacant space 

 which still exists in the neck of the sac. The excretory duct 

 once plngged, the secretion cannot escape, and a whole series of 

 disorders of the hair-sacs, due to retained secretions, are the 

 result. These we will now proceed to describe. 



§ 328. Pausing for a moment to consider the etiology of 

 retention, we find tliat a closure of the hair-follicle by dirt from 



