

CONNECTIVE TISSUE. 169 



appearance found between epithelial layers f. i., between the 

 root-sheaths of the hair. 



Elastic membranes certainly are not structureless, but exhibit 

 a reti<5ulum of living matter of extreme delicacy, concealed in 

 the fresh condition by the highly refracting elastic basis-substance. 

 I am positive that such a reticulum is present in Bowman's and 

 Descemet's layers of the cornea. By means of this reticulum, the 

 connective tissue is held in living union with the epithelium. 

 Such membraneous formations may vary greatly in width, even in 

 the same tissue, f. i., the cornea, and sometimes they may be 

 entirely absent. They, when present, resist the action of acids 

 and alkalies, and, to some extent, the inflammatory process. 



Elastic membranes of the connective-tissue series are the fol- 

 lowing: Bowman's layer at the outer and Descemet's layer at 

 the inner surface of the cornea; the capsule of the crystalline 

 lens and the hyaloid membrane of the vitreous body ; the layer 

 between the outer root-sheath and the follicle of the hair ; the 

 elastic layer beneath the endothelial coat of larger arteries ; and 

 the investing, sometimes fenestrated, layers beneath epithelia of 

 glands f. i., the salivary, the mammary glands. In the kidneys, 

 the connective tissue of the capsule of the tuft, also that which 

 lies between the tubular formations, contains a large amount of 

 elastic substance, which produces a very firm support for the 

 epithelia. 



The striated muscle-fibers, with the exception of those of the 

 heart, are invested by an elastic membrane, termed sarcolemma ; 

 so are the medullated nerves around the axis-cylinder and around 

 the myeline i. e., axis-cylinder sheath and myeline sheath. 



(f) Lamellated Layers of Fibrous Interlacing Connective Tissue. 

 The only representative of this variety is the cornea of the eyeball, 

 the basis-substance of which, although morphologically closely 

 allied to that of elastic substance, is chemically different from 

 both " elastine" and " chondrine." A. Rollett (1859) proved that 

 the " amorphous " basis-substance of former histologists consists 

 of bundles of connective tissue, which are connected by a kind 

 of cement-substance soluble in lime-water and in baryta-water. 

 The main feature of the cornea is that the bundles join to form 

 very thin flat layers, the lamellae; while these lamellae them- 

 selves are connected by somewhat looser bundles, traversing the 

 less condensed interstices between them. 



In the fresh cornea no trace of plastids (cornea corpuscles) is 

 visible ; but if the cornea be kept in an indifferent liquid, after a 



