EXAMINATION OF THE RBSPIRATOEY ORGANS. 657 



tearing, with the aid of fine needles, separate cells may be readily 

 obtained.'" (Fig. 350.) 



The sarcolemma is best seen in the long muscular fibres of 

 the fin of the skate, by tearing them apart with delicate needles 

 and spreading them out upon a piece of glass. In the heart 

 the sarcolemma is so thin that it can scarcely be detected. Some 

 observers doubt its existence (Fig. 351). 



EXAMINATION OP THE EESPIRATORY ORGANS. 



Healthy Lung. — The mucous membrane of the trachea and 

 bronchial tubes, and the 



parenchymatous struc- ^'o- 352. 



ture of the lung may be 

 readily examined by cut- 

 ting thin sections with 

 a very sharp knife, 

 moistening them with 

 water and spreading 

 them out upon slips of 

 glass in the ordinary 

 manner. To examine 

 the ciliated epithelium, 

 and the characteristic 

 movements of the cilia, 

 the air-passages should 

 be scraped and the 

 mattei's thus obtained 

 softened with serum in- 

 stead of water, and de- 

 posited upon glass. The 

 ciliary motion is well 

 displayed in the branchiae 

 of the mollusca, as the 

 oyster. The yellow elas- 

 tic tissue of the lung is rendered quite distinct by the addition 

 of acetic acid (Fig. 352). 



To examine the vascular tissue, the lung should be injected 

 with a somewhat thick solution of transparent gelatine. This 

 oozing through the walls of the vessels, fills and expands the 

 air-cells so that their forms and arrangement can be easily de- 

 tected, while the vessels are seen in their natural position, and 

 apparently deprived of epithelium (Fig. 353). 



An excellent idea of the characteristic appearance of the 

 tracheae of insects, may be obtained by separating with fine 

 needles the viscera of a fly, placing them on a glass slide, and 

 adding a few drops of water. 



' Beale. The Microscope, and its application to clinical medicine. 



42 



a, epithelium; 6, elastic trabeculas; c, membranous wall, 

 with fine elastic fibre. 



