INTERCELLULAR SUBSTANCE. [ 365 ] 



INTESTINES. 



worth notice : — The existence of an inter- 

 cellular substance was first spoken of by 

 Moldenhawer and Agardh. Mohl gave it 

 this special name, and in 1836 declared 

 that it exists very generally, often in large 

 quantity. More recently he has shown that 

 most of what he formerly called by this 

 name consists of secondary deposits. But 

 a kind of cementing matter does seem to 

 exist in very small quantity in some cases, 

 as between the wood-cells of Pinus, &c., 

 which resists all attempts to reduce it into a 

 condition wherein iodine will colour it blue. 

 Valentin regarded the so-called intercellular 

 substance as composed of a series of layers 

 deposited on the outside of the cell-wall. 

 Meyen at first described the solid masses 

 between the cells of collenchymatous tissue 

 as intracellular, subsequently, however, as 

 intercellular productions. Schleiden de- 

 scribes the so-called intercellular masses, 

 like the cuticle, as a secretion from the 

 outside of the cell-wall. Mulder and Harting 

 believe in the existence of this matter, but 

 doubt whether it exists universally. Hartig 

 regards it as an extracellular secretion. 

 Wigand denies the external secretion alto- 

 gether, and declares the so-called intercel- 

 lular substance to consist of the walls of the 

 parent-cells, more or less softened and con- 

 verted into a cement, analogous in its cha- 

 racter to the gelatinous matter of the fronds 

 of Palmellace^. Cohn appears to be 

 of the same opinion. Schacht declares that 

 it exists universally as a cement fastening 

 the cells together, and describes it in the 

 wood of Coniferae, in the leaves of Mosses 

 and Hepaticae, &c., but acknowledges the 

 truth of Mohl's interpretation of the col- 

 lenchyma and so-called intercellular sub- 

 stance of endosperms, &c., which indeed is 

 beyond all doubt. See Epidermis and 

 Secondary deposits. Wood and Albu- 

 men. 



BiBL. Mohl, the papers cited underCELL- 

 MEMBRANE; Valentin, Repertorium, 1836, 

 i. p. 96; Meyen, Pflanzen-jyhysiologie, i. 

 p. 160, Wiegmann's Archiv, 1835, p. 151, 

 ibid. 1837, p. 30; Schleiden, Grundziige, 

 3rd ed. i. p. 330, Transl. [Principles) ^.\ 12 ; 

 Unger, Grunziige der Anat. u. Phys. der PJi. 

 Vienna, 1846, p. 18; Mulder & Harting, 

 Physiological Chemistry (Edinburgh, 1849), 

 pp. 399, 469; Hartig, Ann. des Sc. nat. 

 2 ser. V. ; Wigand, Intercellular-substanz, 

 &c., Brunswick, 1850; Cohn, de Cuticula, 

 LinncBa, xxiii. p. 337, 1850; Schacht, Pjian- 

 zen-zelle, Berlin, 1852, p. 7^' 



INTESTINES.— The intestines consist 

 of three coats, an outer peritoneal (Perito- 

 neum), an inner or mucous membrane, and 

 an intermediate muscular coat. 



The areolar tissue of the mucous mem- 

 brane is often indistinctly fibrous, especially 

 its inner portions, where it forms the base- 

 ment membrane ; it contains scattered, 

 roundish, elongate nuclei, without elastic 

 tissue. Between the proper mucous mem- 

 brane and the submucous tissue, is situated 

 a layer of longitudinal and transverse un- 

 striped muscular fibres, frequently, however, 

 indistinct in man. 



The epithelium of the intestines consists 

 of a single layer of cylindrical cells, contain- 

 ing a transparent oval nucleus, with one or 

 two nuclei, and granular matter. 



The surface of the small intestines is 

 covered with Villi, which are absent in the 

 large intestines. 



Fig. 373. 







■■:9 



Magnified 60 diameters. 

 Perpendicular section of the wall of the lower part of 

 the ileum of the calf, a, villi; b, Lieberkuhn's glands ; 

 c, muscular layer of the mucous membrane ; d, follicle of 

 a Peyer's gland; e, subjacent portion of the submucous 

 tissue ; /, circular muscular fibres ; g, longitudinal ditto. 



