20 MUSCULAR TISSUE. 



this description, perhaps you may be able to recognise it 

 in a quarter of beef or a shoulder of mutton. 



Emily. I presume it is that delicate, white expanded 

 substance which we see in various portions of its surface ; 

 and when I pull asunder the fibres of the red parts of 

 the meat, it appears in the form of very minute and 

 hardly perceptible threads, passing between the fibres 

 and connecting them together. 



Dr. B. Yes ; and these red parts which constitute 

 the chief portion of meat, are formed by the second, or 

 muscular tissue. These fibres, if you will take the 

 trouble to trace them out, will be found to be of consid- 

 erable length, and arranged parallel to one another. A 

 mass of these fibres completely enclosed and separated 

 from the rest, in a sheath of cellular tissue, constitute 

 what is called a muscle. 



Emily. I do not observe this sheath which you speak 

 of it must have been removed from these muscles. 



Dr. B. You may not see it, perhaps, since it is so 

 exceedingly thin and closely applied ; but it really is 

 present. If you move your finger carefully over it, you 

 will find it smooth and slippery very different from the 

 sensation produced by the irregular surface of the naked 

 muscular fibres. The fibres themselves are found to be 

 composed of fibres still smaller ; and if our powers of 

 vision were sufficiently great, we might find these to 

 be made of others more minute, and so on till we come 

 to the ultimate fibre that which is susceptible of no 

 farther division. 



Emily. But does the muscular tissue always exist, 

 as it does here, in the form of long, thick masses? 



Dr. B. No ; these constitute but a portion of all this 

 tissue which may be found in the body. It sometimes 

 appears in a membranous form ; that is, in thin, broad 

 expansions ; in a tubular form, it serves for one of the 

 coats of all the blood-vessels, and is found answering the 

 same purpose in the gullet, stomach and other cavities 

 that require occasional distension. 



