1644 HUMAN ANATOMY. 



fibres has been demonstrated from which terminal fibrillae are distributed to the mus- 

 cular tissue and vessels, as well as beneath the epithelium. 



THE DUODENUM. 



The duodenum at an early stage is a loop with a forward convexity passing from 

 the pylorus back to the spine. It enlarges into nearly a circle and turns onto its 

 right side, its termination remaining attached below the cceliac axis to the top of the 

 second lumbar vertebra. The part immediately following the stomach remains free, 

 but a little farther back it is suspended from the liver by the duodcno-hepatic ligament, 



which is the free border of the lesser 



FIG. 1398. omentum, containing the portal vein, 



Pylorus the hepatic artery, and the bile-duct 



x-^x with the connective tissue about them. 



Pyl ? rus /^||ki J> 4 This structure is strong enough to de- 



/ ';. '-'^ i serve to be called a ligament. The 



*'\ '-, duodenum is therefore nearly a ring sus- 



(*. ^- ; ; L / pended at two points, one near the 



i*^r ! ;>' ^r^jF beginning and the other (to be de- 



. *". -jj scribed later) at the end. In the adult 



W -I v ^ JF W the shape is more or less a modification 



of this imperfect ring. When relaxed 



Casts of duodenum, showing U- and v-forms. and empty it often nearly retains this 



shape. When distended by inflation 



or injection it usually shows four parts. The first, some 5 cm. (2 in.) long, runs 

 backward from the pylorus, slightly upward and to the right. The beginning of 

 this portion is movable ; later the part is fixed by the structures just mentioned. 

 The other divisions of the duodenum are disposed so as to form a U. The second 

 part descends along the right of the spine to the fourth lumbar vertebra. The third 

 runs forward and to the left, with a slight rise. The fourth ascends on the spine to 

 the upper part of the second lumbar vertebra, where, after a sharp bend, the 

 duodeno-jejunal flexure > it becomes the jejunum. 



The next most common form is the V-shaped, of which there are two varieties. In the 

 more usual one the second part descends, as in the preceding form, and the third and fourth 

 are represented by one which ascends obliquely to the termination. The less frequent variety 

 has the second part inclining forward and to the left as it descends, so that the V is more sym- 

 metrical. A modification of the U-form, which we have called the C-shaped, is characterized by 

 a very short second part, so that the first and third parts are almost in contact. From seventy 

 observations 1 on adults (including one girl of fourteen), mostly by means of casts, we find the 

 following forms : 



Male. Female. Sex not noted. 



U-shaped 10 3 9 



V-shaped 9 9 



Ring-shaped 2 2 



Indeterminate 7 3 i 



C-shaped 5 



Not to be classified 5 . . 2 



38 I? 15 



By "indeterminate" is understood those that might be placed in any two of the U, V, or C 

 types, according to the classifier. Those marked " not to be classified" are absolutely irregular. 

 The Y -shape is particularly common in women and the irregular forms in men. It should be 

 noted that .i very large part of the duodenum lies in an essentially antero-posterior plane. 

 namely, the first, second, and a considerable portion of the third part, the organ being moulded 

 on the spinal column. Tin- length of the whole duodenum and of its parts is so variable that a 

 statement can be only general. The first part is, according to Testut, 5 cm., the second S cm., the 

 third 6 cm., and th- fourth 7 cm., the total length of the duodenum being 26 cm., or about 

 i m. The circumference varies greatly in different bodies. The fourth part is the smallest. 

 'I he second increases in si/<- as it descends, and the largest point is in either the second or third. 

 I lie two largest circumferences that we have measured were in the second part. We are sat-. 

 fefied that the size of some immense duodena is in no way due to artificial distention ; to what 

 extent it is pathological is uncertain. 



1 Journal of Anatomy and Physiology, vol. xxxi., 1897. 



