12S8 THE SKIN, MAMMARY GLANDS AND DUCTLESS GLANDS 



The amount of elastic tissue mixed with the white fibrous connective tissue of which the 

 corium and subcutaneous tela mainly consist varies in the different parts of the body. It is 

 especially abundant in the deeper layer of the tela over the caudal part of the ventral ab- 

 dominal wall where it forms almost a continuous sheet. Many elastic fibres also accompany the 

 blood-vessels and are mingled with the connective-tissue sheaths around the hairs, the sweat 

 glands, and their ducts. '^ 



The papill(E corii are usually simple cones but some are bulbous at their ends and others 

 have duplicated apices. They may be perpendicular to the surface or oblique, in some places 

 overlapping. Those on the flexor surfaces of the hands and feet are best developed and are 

 arranged in rows so as to form long parallel curvilinear ridges, two of which are grouped together 

 and correspond to one crista on the surface of the epidermis (figs. 1045, 1046). When there are 

 no papillary ridges the papillte are irregularly scattered, shorter, and may disappear in places 

 or be replaced by ridges. The papillae serve to give a greater surface area to the corium so as 

 to bring a greater number of blood-vessels and nerves into closer relation with the epidermis and 

 thus with the surface of the body. They are best developed where the epidermis is thickest. 

 Thus the}' are the largest on the flexor surface of the hands and feet and beneath the nails and 

 are smallest on the face, scrotum, and mamma?. 



The skin, as removed in the dissecting room, usuallj^ includes the epidermis and more or 

 less of the corium and subcutaneous tela. The cut surface is formed of connective tissue which 

 kas a shining bluish-white appearance with minute pits closely scattered over the surface. 

 These pits are usually more or less completely filled with small yellow fat lobules. 



Skin muscles. — In the subcutaneous tela and the corium muscle fibres are 

 found in large and small groups. These are of two kinds, striated muscle and 

 unstriated muscle. 



Subcutaneous planes of striated muscle are relatively scanty in man when compared with the 

 great panniculus carnosus of the lower mammalia. This is mainly represented by the platysma 

 in the neck which has both its origin and part of its insertion in the skin. Closely associated 

 with this are the muscles of expression of the face and the palmaris brevis muscle which have 

 one end terminating in the deep surface of the skin. The epicranial muscle is also considered by 

 some to belong to this group. 



Unstriated muscle fibres are scattered through the corium collected into bundles in the 

 neighbourhood of the sebaceous glands and the hairs. They are described in connection with 

 these latter (p. 1293). In addition to these unstriated muscles are found in the scrotum as the 

 dartos, in the perineum, around the anus, and beneath the papilla and areola of the mammary 

 gland. 



BursaB mucosae subcutanea. — In some situations where the integument is 

 exposed to repeated friction over subjacent bones or other hard structures its 

 movements are facilitated by the development of sac-like interspaces in the sub- 

 cutaneous tissue, the subcutaneous mucous bursas. They are similar to the more 

 deeply placed bursse which are found in relation with muscle tendons. Their 

 occurrence is quite variable. In some individuals they are numerous, in otliers 

 very few. They have a considerable practical importance from the fact that they 

 may become greatly swollen. 



The most constant subcutaneous mucous bursiu are the following: 



Bursa anguli mandibulae; B. subcutanea prementalis, between the periosteum and soft parts 

 over the tip of the chin; B. subcutanea prominentiag laryngeae over the ventral prominence of 

 the thyreoid cartilage of tlie larynx (often found in the male; B. subcutanea acromialis, between 

 the acromion and the skin; B. subcutanea olecrani, beneath the skin on the dorsal surface of 

 the olecranon; B. subcutanea epicondyli humeri lateralis, found beneath the skin over the 

 lateral epicondyle of tlie humerus (occasional); B. subcutanea epicondyli humeri medialis, 

 between the skin and the medial epicondyle of tlie humerus (more frequent); B. subcutanea 

 metacarpophalangea dorsalis, between the skin and the dorsal side of the metacarpophalangeal 

 joints (occasional, especially the fifth); B. subcutanea digitorum dorsalis, beneath the skin over 

 the proximal finger-joints; and rarely over the distal finger-joints; B. subcutanea trochanterica, 

 between the skin anrl the great trochanter of the femur; B. subcutanea praepatellaris, beneath 

 the skin covering tlio caudal half of the jjatella; B. subcutanea infrapatellaris, between the skin 

 and the cephalic end of the ligamcntum patelhr; B. subcutanea tuberositatis tibiae ventral to 

 the tibial tuberosity, covered by skin or by skin and crural fascia; B. subcutanea malleoli 

 lateralis, between the skin and the i)oint of the latcnal malleolus; B. subcutanea malleoli me- 

 dialis, between the skin and medial malleolus; B. subcutanea calcanea, in the sole of the foot 

 between the skin and the i)lantar surface of tlie calcancum; B. subcutanea sacralis, beneath 

 the skin which covers the lumbodorsal fascia and the region between the sat-rum and coccyx. 



Blood-vessels of the skin. — Both the corium and the subcutaneous tela are very vascular, 

 hut the size and nnrnber of vessels varies in different situations. Although the origin of the 

 cutaneous arteries from the deep arteries and the positions whore tlie subcutaneous arteries 

 ])i(!rf-(; the inusfles vary greatly, the areas sup))li(;(i by ccniain groups of arteries and the direc- 

 tion in which the arteries of the skin nm show niu(;h regularity. Moreover the metameric 

 arrangement of the arteries in the skin is clearly seen, especially upon (he trunk. We can recog- 

 nise two groups of skin arteries. One grf)up is represented by a small number of rather large 

 branches which are distributed throughout or princijjally in the subcutaneous tela and corium, 

 as the inferior superficial epigastric artery, the arteries of the scalp, etc. These arteries tend to 



