I590 HUMAN ANATOMY. 



Cleft palate is caused by faulty union between the palatal processes of the maxillary 

 arches. The cleft is always in the middle line, and may involve only the uvula and 

 soft palate, may extend to the posterior margin of the intermaxillary bone, or may 

 diverge from that point on one or both sides and run forward through the alveolus, 



being then associated with single or double hare- 

 X iG. 1350. jjp^ j-j^g cleft or clefts in the alveolus corresponding 



in position to the deficiencies in the lip (page 63). 

 , The Lips, — The mucous membrane of the 



lips and the adjacent skin are often affected by 

 herpes labialis, which may be associated with 

 gastro-intestinal disturbance, or may be purely 

 neurotic in its origin, following mental depression 

 or anxiety. It is found in the distribution of the 

 second and third divisions of the fifth pair which 

 supply sensation to the upper and lower lips re- 

 spectively. The vascularity of the lips, while it 

 leads to excessive exudate and large swelling after 

 contused or lacerated wounds, favors rapid heal- 

 ing and the avoidance of infection after surgical 

 wounds. In few places equally exposed to con- 

 New-born child with double harelip. tact with infectious orgauisms was healing by ' ' first 



intention" so common before the introduction of 

 antisepsis. The coronary arteries run between the mucous membrane and the orbicu- 

 laris oris. They are therefore more often severed by wounds extending from within 

 outward — usually made by the teeth — than by those beginning externally. The coro- 

 naries anastomose very freely. In arresting hemorrhage from them by direct ligature 

 both ends should be tied. If a wound of the lips is united by pins and figure-of- 

 eight sutures, the pins should be passed close to the inner edges 6f the wound so that 

 the coronaries may be compressed between the pins and the sutures. The vascu- 

 larity of the lips renders chancres of that region, like those of the face, exceptionally 

 large both in depth and in superficial area. It also adds greatly to the extent of 

 furuncular or carbuncular infection in this region, the occurrence of which is favored 

 by the large number of hair and sebaceous follicles present. The danger of infective 

 sinus thrombosis (intracranial) as a result of such infection here or elswhere on the 

 face is much increased by the free anastomosis between the valveless facial vein and 

 its tributaries and the ophthalmic vein, which is also without valves. As might be 

 expected, naevi are frequent in the lips. In the male the lower lip is the favorite seat 

 of epithelioma. Either infection or diminished tissue resistance from minor trauma- 

 tisms, or from tobacco-irritation in smokers, is supposed to explain this clinical fact. 

 The mucous glands of the lip are not rarely the seat of retention-cysts from obstruc- 

 tion of their ducts. 



The Gums. — The mucous membrane of the lips is continuous with that cover- 

 ing the fibrous tissue of the gums, but the latter is slightly less vascular and much less 

 sensitive. The gums are sometimes congenitally hypertrophied ; the condition is 

 usually associated with defective or aberrant developmental processes often affecting 

 the mentality. They are also often found hypertrophied in edentulous old persons or 

 in persons with badly fitting artificial dentures. They are the frequent seat of inflam- 

 mation from various causes, the most common of which are the decomposition of 

 food and the deposition of calcium salts — tartar — about the necks of the teeth. Infec- 

 tion frequently follows the hyperaemia produced by these forms of irritation. When 

 it is confined to the space between the mucous membrane and the fibrous tissue, it 

 causes a limited superficial abscess, — "gum-boil;" if it gains access to the sub- 

 periosteal space, it may cause a form of alveolar abscess, the usual variety of which 

 is, however, due to infection secondary to dental caries, and is situated about the root 

 of a tooth {vide infra). 



Tartar is found most abundantly near the openings of the submaxillary and sub- 

 lingual ducts, — i.e., near the inner surfaces of the lower incisor teeth. Mercury and 

 lead cause gingivitis probably by the actual presence of their salts in quantity suffi- 

 cient to act as irritants, their deposition from terminal capillaries being favored by the 



