SPLEEN. 



[ 602 ] 



SPONGIiE. 



arise from the inner surface of the fibrous 

 coat and from the outer surface of the vas- 

 cular sheaths ; and being connected with 

 each other, form a number of irregular 

 meshes or areolae, in which are situated the 

 splenic corpuscles and the spleen-pulp. 



The fibrous coat and the trabeculse consist 

 of ordinary areolar tissue, with mostly 

 parallel fibres, traversed by networks of fine 

 elastic fibres. In certain animals, as the 

 dog, cat, pig, &c., the fibrous coat and tra- 

 beculse contain also unstriped muscular fibres. 

 These do not occur in man, unless they are 

 represented in the microscopic trabeculse by 

 peculiar wavy fibres, about 1-500" in length, 

 with lateral or stalked nuclei (fig. 680). 

 Some of these are found enclosed in cells 

 (fig. 681), from which they become liberated 

 by the action of water. 



The splenic or Malpighian corpuscles 

 (fig. 682) are white rounded bodies, imbedded 

 in the spleen-pulp, and attached to the 

 smallest arteries. They vary in size from 

 l-120tol-36",and cannot always be detected. 

 They are either placed upon the sides of the 

 arterial branch, or situated in the angles of 

 their bifurcation. 



The splenic corpuscles consist of an enve- 

 loping membrane (fig. 683 a) composed of 

 areolar tissue, with fine reticular elastic 

 fibres, and derived from the arterial sheath. 

 They are traversed by capillaries and filled 

 with a tenacious gray mass, consisting of an 

 albuminous liquid, with cells 1 -3000" in dia- 

 meter, containing one or two nuclei, and free 

 nuclei (fig. 108, p. 114). Sometimes the 

 cells contain globules of fat or blood-cor- 

 puscles, and occasionally free blood-corpus- 

 cles are met with. 



The spleen-pulp forms a soft reddish mass 

 and consists of three elements, microscopic 

 trabecule, fibres or bands, parenchyma-cells, 

 and the smaller blood-vessels. The trabeculse 

 agree in structure with the larger ones. The 

 fibres or bands are the terminations of the 

 sheaths of the vessels ; they are indistinctly 

 fibrous and free from elastic tissue. The 

 parenchyma-cells resemble those in the 

 splenic corpuscles. Extravasated blood is so 

 frequently met with in the parenchyma that 

 its presence may be regarded as normal, and 

 the blood-corpuscles are found enclosed in 

 cells, from one to twenty in each, or sur- 

 rounded by a transparent substance, their 

 contents exhibiting various changes in colour 

 and consistence. The arteries terminate in 

 elegant tufts or penicilli, becoming conti- 

 nuous with a mesh-work of capillaries. 



The blood -corpuscles from the blood of J 

 the splenic vein frequently contain crystals 

 of heematoidine. 



In the examination of the spleen, the tra- 

 becule are best seen after washing away the 

 pulp with water ; the splenic corpuscles by 

 tearing the spleen, or boihng it ; either in 

 the pig or ox. The cells containing blood- 

 corpuscles must be searched for in the pulp 

 unacted upon by water. The muscular fibres \ 

 are most evident in the smaller trabeculse, 

 especially after treatment with dilute nitric 

 acid (one part to five parts of water). 



BiBL. Kolliker, Mikrosk. Anat. ii. 253, 

 and Todd's Cycl. Anat., Sfc, art. Spleen ; 

 Gray, A. Cooper^ s Prize Essay, Saunders, 

 Goodsir's Annals of Anat. ^c. 1850. i. ; 

 Crisp, On the Spleen. 



SPONGIiE (Sponges). — An order of Ani- 

 mals, belonging to the class Protozoa. 



Char. Form variable ; fixed by a kind of 

 root at the base, or encrusting; consisting 

 of a soft gelatinous mass, mostly supported 

 by an internal skeleton composed of reticu- 

 larly anastomosing horny fibres, in or among 

 which are usually imbedded siliceous or cal- 

 careous spicula; or sometimes the spicula 

 alone form the skeleton. 



The horny fibres forming the skeleton of 

 sponges, which may be well seen in any 

 common sponge, are cylindrical, and va- 

 riously united, so as to form a coarse net- 

 work with roundish or angular microscopic 

 meshes. In addition to these generally dif- 

 fused meshes or intervals, large (to the naked 

 eye) rounded apertures (oscula) are scattered 

 over the surface of most sponges, leading 

 into sinuous canals permeating their sub- 

 stance in every direction; and between these 

 are other smaller apertures, just visible to 

 the naked eye, also the orifices of canals, 

 which traverse the substance and communi- 

 cate with the oscular canals. 



In the living sponge this skeleton is co- 

 vered with a glairy or gelatinous, colourless, 

 amorphous substance, resembling that of 

 which the Amoebce are composed, but some- 

 times more liquid ; the proportion of which 

 is variable in the diflPerent genera. This 

 substance appears to be composed of minute 

 masses, those on the surface being furnished 

 with long and very slender vibratile cilia; 

 and during life, by means of these, water 

 entering by the smaller apertures, and reach- 

 ing the oscular channels, is expelled from the 

 oscula in currents, which may be rendered 

 visible by sprinkling a little finely powdered 

 charcoal over them. If detached portions 



