274 



THE MICROSCOPE AND ITS REVELATIONS. 



FIG. 463. 



way penetrates and forms part of all the softer organs of the body. But 

 whilst the fibrous structures of which the * formed tissue ' is composed 

 have a purely mechanical function, there is good reason to regard the ' con- 

 nective-tissue-corpuscles ' which are every where dispersed among them, as 

 having a most important function in the first production and subsequent 

 maintenance of the more definitely organized portions of the fabric ( 650). 

 In these corpuscles, distinct movements, analogous to those of the sarco- 

 die extensions of Ehizopods, have been recognized in transparent parts, 

 such as the cornea of the eye and the tail of the young Tadpole, by ob- 

 servations made on these parts whilst living. For the display of the 

 characters of the fibrous tissues, small and thin shreds may be cut with 

 the curved scissors ( 183) from any part that affords them; and these 



must be torn asunder with needles under 

 the simple Microscope, until the fibres are 

 separated to a degree sufficient to enable 

 them to be examined to advantage under a 

 higher magnifying power. The difference 

 between the ' white ' and the ' yellow ' com- 

 ponents of connective tissue is at once 

 made apparent by the effect of Acetic acid ; 

 whilst the ' connective-tissue-corpuscles ? 

 are best distinguished by the staining-pro- 

 cess ( 200), especially in the early stage of 

 the formation of these tissues (Fig. 461). 



670. Skin; Mucous and Serous Mem- 

 branes. The Skin which forms the external 

 envelope of the body, is divisible into two 

 principal layers ; the cutis vera or ' true 

 skin,' which usually makes up by far the 

 larger part of its thickness, and the ' cuticle/ 

 ' scarf-skin,' or epidermis, which covers it. 

 At the mouth, nostrils, and the other orifices 



n f J.I, P nrtp t pavifipc jmrl pnvil nf flip hnriv 

 C C tne . P en ca ?dy, 



the skin passes into the membrane that lines 

 these, which is distinguished as the mucous 

 membrane from the peculiar glairy secretion 



Vertical Section of Skin of Finger: 

 A, epidermis, the surface of which 



shows depressions a, a, between the 



, 



which are imbedded the perspiratory OI milCUS by which its SUriaCC IS protected. 

 glands d, with their ducts e, and ag- T> n f 4-VincP o-rpaf rlr\<iPil pnx'iHpa nf flip IWlv 

 gregations of fat-cells/; <?, arterial - tJut tUOSe gieat CtOSea Ca\ltieS OI tlie OCly, 



twig supplying the vascular papillae which surround the heart, lungs, intes- 

 ftinerv n el ofth6tact ' lepal " Uew ' u ' tines, etc., are lined by membranes of 



different kind; which, as they secrete 



only a thin serous fluid from their surfaces, are known as serous membranes. 

 Both Mucous and Serous membranes consist, like the skin, of a proper 

 membranous basis, and of a thin cuticular layer, which, as it differs in 

 many points from the epidermis, is distinguished as the Epithelium 

 (673). The substance of the 'true skin 'and of the ' mucous' and ' serous r 

 membranes is principally composed of the fibrous tissues last described; 

 but the skin and the mucous membranes are very copiously supplied with 

 Blood-vessels and with Glandulae of various kinds; and in the skin we 

 also find abundance of Nerves and Lymphatic vessels, as well as, in some 

 parts, of Hair-follicles. The general appearance ordinarily presented by 

 a thin vertical section of the skin of a part furnished with numerous sen- 

 sory papillw ( 682), is shown in Fig. 463: where we see in deeper layers of 

 the cutis vera little clumps of fat-cells, /, and the perspiratory glandulae, 



