SECT. 



28.] MUSCULAR TISSUE. 63 



3. Muscular Tissue. 



§ 28. General Characters. — The further our knowledge of the 

 contractile tissues advances, the more clearly does it appear that 

 the decided separation, hitherto assumed to exist between smooth 

 and transversely striped animal and organic muscular fibres, can 

 no longer be maintained. For besides the well-known fact, that 

 the animal muscular fibres of certain creatures do not, in any 

 respect, differ in structure from smooth muscles, inasmuch as they 

 consist of a homogeneous substance, without either fibrils or striee, 

 it has also been shown that smooth muscles exist, whose elements 

 are transversely striated, like the animal muscular fibres of the 

 higher animals. Moreover, the mode of development of the con- 

 tractile tissues and their physiological phenomena are by no means 

 favourable to a division of them in the accustomed sense. With re- 

 gard to the former, it follows, from the observations of Lebert andife- 

 mak on the muscles of frogs, and from mine on those of mammalia, 

 frogs, and many invertebrata, that even the long, striated muscular 

 fibres are nothing else than single cells (see below) ; and, therefore, 

 the old distinction between muscular fibres formed by single cells, 

 and fibres representing many cells, cannot longer be maintained. 



Nor is the case different in a physiological point of view, seeing 

 that it can scarcely be doubted, that the essential distinctions ob- 

 served in the functions of the animal and organic muscles depend 

 only on their relations to the nervous system. Since, moreover, 

 no differences in chemical constitution are known between the 

 various contractile elements, it appears, on every ground, reasonable 

 to place them together in one group. Nevertheless, it appears to 

 me advisable, especially with reference to the muscles of man and 

 the higher animals, to retain the two well-known designations in 

 order to indicate the subdivision of this group, and to employ 

 the mode of development as the principle of division. For al- 

 though a great diversity exists in the form of the contractile 

 elements, yet it is obvious, that the great majority of them are 

 divisible into two classes: 1. those which consist of a cell with 

 one nucleus; and 2. those which contain a great number of nuclei. 

 Now, since the most important distinction, which, apart from their 

 relation to the nervous system, prevails between the contractile 

 elements is, perhaps, connected with this difference, — the distinc- 

 tion, namely, that the one class of muscles are capable of limited 

 and independent contractions, even in their smallest portions, 

 while the other are capable only of total contraction, I am the 



