526 THE MICROSCOPE. 



to be made up of fine longitudinal fibres only. The 

 microscope tells us that each of these supposed fine fibres 

 is composed of numerous smaller ones, and that these are 

 crossed by lines which have received the name of transverse 

 striae; that muscular contraction, the cause of motion in 

 animals, is produced by the relaxation or approximation 

 of these transverse striae. 



The microscope has shown us that a distinct network of 

 vessels lies between the arteries and veins, partaking of 

 the properties of neither, and possessed of others peculiar 

 to themselves. These have been denominated intermediary 

 vessels by Berres, and serve to connect the arterial with 

 the venous system. 



On regarding with the naked eye the different glands 

 in which the secretions are formed, how complex they 

 appear, how various in conformation! The microscope 

 teaches us that they are all formed on one type ; that the 

 ultimate element of every gland is a simple sacculated 

 membrane, to which the blood-vessels have access; and 

 that all glands are formed from the greater or less number, 

 or different arrangement only of the primary structure. 



Our notions respecting the skin were vague until the 

 microscope discovered its real anatomy, and showed us 

 the existence and relations of the papillae, of the sudorific 

 organs and their ducts, the inhalent muscular apparatus, 

 and so on. All our knowledge of epidermic structures, 

 such as hair, horn, feather, &c., the real structure of 

 cartilage, bone, tooth, tendon, cellular tissue, and, in a 

 word, of all the solid textures, has been revealed to us by 

 the same agency; so that it may be truly said, that all our 

 real knowledge of structural anatomy, and all our acquaint- 

 ance with the true composition of every organ in the body, 

 have been arrived at by means of the microscope, and 

 could never have been known without it. 



In addition to this, and what is of greater importance, 

 after having studied the healthy structure of the body, 

 most beneficial aid is afforded in the investigation of 

 changes produced by diseases, which were overlooked, or 

 undistinguishable without the assistance of this instrument; 

 it is on this account constantly resorted to by the medical 

 profession for the benefit of their fellow-creatures. 



