334 SECRETION. 



sheath in the liver. The number of the sheaths in the spleen 

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

 This is sometimes called the capsule of Malpighi. 1 The 

 fibrous sheaths are closely adherent to the surrounding 

 substance, but are united to .the vessels by a loose fibrous 

 net-work. They follow the vessels in their ramifications to 

 the smallest branches, and are lost in the spleen-pulp. Be- 

 tween the sheath and the outer coat, are numerous bands or 

 trabeculse of the same structure as the fibrous coat. The 

 presence of elastic fibres in these structures can be easily 

 demonstrated, and this kind of tissue is very abundant in 

 the herbivora. In the carnivora the muscular tissue is par- 

 ticularly abundant, and can be readily demonstrated ; 2 but 

 in man this is not so easy, and the fibres are less numerous. 

 There can be no doubt, however, that muscular tissue exists 

 in the human subject throughout the whole extent of the 

 fibrous structure, and the fibres are demonstrated without 

 much difficulty in the trabeculse. 3 



These peculiarities in the fibrous structure are important 

 in their relation to certain physiological changes in the size 

 of the spleen. Its contractility can be easily demonstrated 

 in the dog by the application of a galvanic current to the 

 nerves as they enter at the hilum. This is followed by a 

 prompt and energetic contraction of the organ. Contrac- 

 tions may be produced, though they are much more feeble, 

 by applying the current directly to the spleen. 4 



The substance of the spleen is soft and friable ; and a 

 portion of it, the spleen-pulp, may be easily pressed out, or 

 even washed away by a current of water. Aside from the 

 vessels and nerves, it presents for study : 1. An arrange- 



1 MALPIGHI, De Liene, Opera Omnia, Lugd. Batav., 1687, tomus ii., p. 294. 



2 Kolliker has demonstrated the presence of muscular fibres in considerable 

 numbers in the dog, pig, ass, and cat ; but they were not discovered in the rab- 

 bit, horse, ox, hedgehog, porpoise, or bat (Handbuch dcr Gewebelchre, Leipzig, 

 1867, S. 449). 



3 SAPPEY, Traite d'anaiomie, Paris, 1857, tome iii., p. 323. 



4 BERNARD, Lefons sur les liquides deVorganisme, Paris, 1859, tome ii., p. 421. 



