DEEMOIDS. 77 



the mandible and the hyoid bone and between the cricoid and 

 thyroid cartilages. 



The post-oral fissures sometimes develop tubulo-dermoids, which 

 will appear in the anterior triangle of the neck, and are placed 

 beneath the deep fascia. 



The post-anal gut gives rise to two forms of tubulo-dermoids. 

 One, which is ordinarily termed a congenital sacro-coccygeal 

 tumour, projects from between the rectum and the coccyx, and 

 presents characters of both alimentary and nervous tissue. The 

 other lies between the rectum and the hollow of the sacrum, and 

 may sometimes find its way through the rectal wall, and, ulcer- 

 ating, discharge its contents through the anus. 



Ovarian and Testicular Dermoids. It is particularly interest- 

 ing that there may be associated with the ovary and with the 

 testis a species of tumour which has all the characteristics of a 

 dermoid. In connection with the ovary they probably arise 

 from the oophoron, or that portion of the organ which develops 

 the follicles, and are probably due to cells which were originally 

 connected with epiblast. They are therefore essentially the 

 resultant of a true embryonic intrusion into the ovary, and may 

 stand in close relation to teratomata or parasitic foetuses. 



Dermoid tumours of the testis must not be confounded with 

 scrotal dermoids, that is, those sequestration dermoids which are 

 to be found in the middle line of the scrotum in the raphe 

 the evidence of the original fusion of its two halves. There 

 appear to be true dermoids of the testis proper, developed in 

 probably the same manner as dermoids of the ovary, namely 

 from a misplaced portion of epiblastic embryonal tissue. 



Dermoid Patches, or hairy moles. These are essentially moles, 

 or rather hairy moles. It is questionable whether all moles 

 should be classified as dermoid patches, but those which occur 

 in the middle line and in the lines of congenital fissures, as 

 for instance in the line of the fissure between the maxillary 

 process and the mandibular arch, are certainly of such a 

 character. Hairy moles are also seen on the limbs and on 

 the conjunctiva. 



