414 USES OF THE LIVER DUCTLESS GLANDS. 



nerves. It is connected with the stomach by the gastro-splenic omentum and 

 is still farther fixed by a fold of peritoneum passing to the diaphragm. It is 

 about five inches (127 mm.) in length, three to four inches (75 to 100 mm.) in 

 breadth, and a little more than an inch (25-4 mm.) in thickness. Its weight is 

 six to seven ounces (170 to 198 grammes). In the adult it attains its maxi- 

 mum of development, and it diminishes slightly in size and weight in old age. 

 In early life it bears about the same relation to the weight of the body as in 

 the adult 



The external coat of the spleen is the peritoneum, which is very closely ad- 

 herent to the subjacent fibrous structure. The proper coat is dense and resist- 

 ing, but in the human subject it is quite thin and somewhat translucent. It 

 is composed of ordinary fibrous tissue mixed with abundant small fibres of 

 elastic tissue and a few unstriped muscular fibres. 



At the hiluni the fibrous coat penetrates the substance of the spleen in 

 the form of sheaths for the vessels and nerves. The number of the sheaths in 

 the spleen is equal to the number of arteries that penetrate the organ. This 

 membrane is sometimes called the capsule of Malpighi. The fibrous sheaths 

 are closely adherent to the surrounding substance but they are united to the 

 vessels by a loose, fibrous net- work. They follow the vessels in their ramifi- 

 cations to the smallest branches and are lost in the spleen-pulp. BetAveen 

 the sheath and the outer coat, are bands, or trabeculae, presenting the same 

 structure as the fibrous coat. The presence of elastic fibres in the trabeculae 

 can be easily demonstrated, and this kind of tissue is very abundant in the her- 

 bivora. In the carnivora the muscular tissue is particularly abundant and 

 can be readily demonstrated ; but in man this is not so easy, and the fibres 

 are less abundant. These peculiarities in the fibrous structure are important 

 in their relations to certain physiological changes in the size of the spleen. 

 Its contractility may be easily demonstrated in the dog, by the application of 

 a Faradic current to the nerves as they enter at the hilum. This is followed 

 by a prompt and enegetic contraction of the organ. Contractions may be pro- 

 duced, though they are much more feeble, by applying the current directly 

 to the spleen. 



The substance of the spleen is soft and friable ; and a portion of it, the 

 spleen-pulp, may be easily pressed out with the fingers or even washed away 

 by a stream of water. Aside from the vessels and nerves, it presents for 

 study: 1, an arrangement of fibrous bands, or trabeculae, by which it is 

 divided into communicating spaces ; 2, closed vesicles, called Malpighian 

 bodies, attached to the walls of the blood-vessels ; 3, a soft, reddish substance, 

 containing large numbers of cells and free nuclei, called the spleen-pulp. 



Fibrous Structure of the Spleen (Trabeculce). From the internal face of 

 the investing membrane of the spleen and from the fibrous sheath of the ves- 

 sels (capsule of Malpighi), are bands, or trabeculae, which, by their interlace- 

 ment, divide the substance of the organ into irregularly shaped, communi- 

 cating cavities. These bands are -fa to ^ of an inch (1 to 1-7 mm.) broad, and 

 are composed, like the proper coat, of ordinary fibrous tissue with elastic 

 fibres and probably a few non-striated muscular fibres. They pass off from 



