62 



THE ESSENTIALS OF HISTOLOGY 



stained, wash it in water and with needles break the fibres up in Farrant's 

 solution into as fine fibrils as possible. Cover and examine with a high 

 power. 



3. Tear off a small shred of the muscular coat of a piece of intestine which 

 has been from 24 to 48 hours in ( per cent.) bichromate of potash solution. 

 Hold the shred with forceps in a drop of water and fray it out with a needle. 

 In this process many cells will be set free and can be seen with a low power. 

 The preparation may then be covered and examined with a high power. 

 Sketch one of the cells. Then allow dilute logwood to pass under the cover- 

 glass and lastly a drop of glycerine. Sketch another cell after staining. 

 Measure two or three cells and their nuclei. 



Voluntary muscle is composed of long cylindrical fibres, measuring 

 on an average about ^^ inch in diameter in mammalian muscles, but 

 having a length of an inch or more. Each fibre has an elastic sheath, 

 the sarcolemma, which encloses the contractile substance. The sarco- 

 lemma is seldom distinct, unless the contained substance becomes 

 broken (fig. 69). 



FIG. 69. SAKCOLEMMA 

 OF MAMMALIAN MUS- 

 CLE, HIGHLY MAGNI- 

 FIED. 



The fibre is represented at 

 a place where the mus- 

 cular substance has be- 

 come ruptured and has 

 shrunk away, leaving the 

 sarcolemma (with a 

 nucleus adhering to it) 

 clear. The fibre had been 

 treated with serum acidu- 

 lated with acetic acid. 



FIG. 70. MUSCULAR 

 FIBKE OF A MAMMAL 

 EXAMINED FRESH IN 

 SERUM, HIGHLY MAG- 

 NIFIED, THE SURFACE 

 OF THE FIBRE BEING 

 ACCURATELY FO- 



CUSSED. 



The nuclei are seen on the 

 flat at the surface of the 

 fibre, and in profile at 

 the edges. 



The contractile substance of the fibre is characterised by the alter- 

 nate dark and light stripes which run across the length of the fibre ; 

 hence the name, cross-striated or striped muscle. On focussing, it 



