WITH THE MICROSCOPE. I I 5 



the supply of the tissue with its proper nutritive elements. In the fifth 

 place we find nerve-fibres running in the same position as the vessels, 

 and lastly, at least in relation with some of the fibres, are lymphatic 

 vessels. The student may refer to plates XXVII and XXVIII. 



Thus, muscle is composed of several elementary structures, each 

 having special anatomical peculiarities, and differing from the others 

 in physical characters and chemical properties. Some of these 

 structures refract light very highly ; others, only in a very slight 

 degree. One may be greatly altered or even destroyed within 

 a very short time after the muscle has been removed from the 

 body, or by the action of plain water, while others resist decompo- 

 sition for a great length of time. The characters of one may be 

 demonstrated when the muscle is examined in water ; a second, when 

 it is immersed in syrup or glycerine ; a third, when the specimen is 

 mounted in Canada balsam ; while the arrangement of the delicate, 

 transparent, capillary vessels cannot be satisfactorily made out unless 

 a particular plan of preparation be adopted, as described in page 90. 



The chemist can detect a number of other compounds the presence 

 of which the microscopical observer might ever remain unconscious 

 of, for they are dissolved in the juices of the muscle, and therefore 

 incapable of being detected by the eye alone. 



The vast difference in the properties of the several textures above 

 enumerated renders it very difficult to demonstrate r.ll in one single 

 specimen, for the circumstances which favour the exhibition of 

 one structure will often render another quite invisible. Hence, 

 before we can hope to demonstrate satisfactorily the anatomical 

 peculiarities of any one of these different textures we must 

 become acquainted with its general properties, and must consider 

 the mode of examination likely to be most efficient in rendering these 

 distinct. 



The walls of the smallest vessels are so thin and transparent 

 that it is necessary to fill them with some coloured fluid or material 

 more or less opaque, if we wish to see the mode of arrangement of 

 the vascular network, while this same process, as ordinarily followed 

 out, precludes the possibility of tracing the finer ramifications of the 

 nerves ; moreover other elementary tissues are hidden and compressed 

 by the distended vessels. To demonstrate the nerves, all the other 

 structures must be rendered as transparent as possible, by the applica 

 tion of a chemical agent, or by immersing the specimen in a highly 

 refracting fluid. In order to show the membrane in which the con- 

 tractile sarcous tissue is contained, the latter must be ruptured within 

 it in a perfectly fresh specimen, or it must be separated from it 

 by pressure. By one plan of proceeding it may be shown that the 



i 2 



