280 OF MUSCULAR CONTRACTILITY. 



a granular arrangement in their interior ; and these markings have occasion- 

 ally a degree of regularity which approaches that of the stria? on the Muscular 

 Fibre of Animal life. In most instances, the nuclei of the cells in which they 

 originate, are very perceptible ; and from their similarity to the imperfectly 

 formed fibres of Animal life, it would seem that they are rather to be com- 

 pared with these than with their fibrillaz, to which some have considered them 

 analogous. These fibres are, like those of the other muscles, arranged in a 

 parallel manner into bands or fasciculi ; but these fasciculi are generally inter- 

 woven into a network, not having any fixed points of attachment, but contract- 

 ing against each other. This kind of structure is that which forms the muscular 

 coat of the oesophagus, stomach, [Fig. 70, (4 and 5,)] intestinal tube, bladder, 

 and pregnant uterus ; it is found, also, in no inconsiderable amount, in the 

 trachea and bronchial tubes. The pharyngeal muscles, however, belong to the 

 former system.* The fibres of the Uterus somewhat differ in aspect from those 

 of other parts ; being much broader at their centre, and tapering off at their 

 extremities into what appear to be cylindrical parts. In the Heart, both the 

 striated and non-striated muscular fibres are found ; and this accords with the 

 structure of the organ, which affords some fixed points, whilst much of its 

 action resembles (except in its greater degree of vigour) that of the muscular 

 coat of the intestines. It is a curious and interesting fact, that in Articulata, 

 whose animal life is so predominant ( 22), the Animal muscular fibre is 

 formed as perfectly as in the highest Vertebrata ; whilst in Mollusca, whose 

 character is exactly the reverse ( 28), scarcely any striated fibres can be 

 detected. It seems probable that the contractility possessed by the skin 

 (which gives rise to the state termed culis anserina, under the influence of 

 cold, or of depressing mental emotions), and that which is peculiar to the 

 Dartos (by which the scrotum is thrown into wrinkles), are alike due to the 

 action of fibres of this description, intermingled with the other fibrous tissues 

 of which these parts are chiefly composed. The middle coat of the Arteries 

 will be hereafter shown to have a strong analogy to this form of muscular 

 tissue, both in structure and properties (Chap. ix). 







IV. Properties of Muscular Fibre. 



376. Muscles may be thrown into contraction, so long as they preserve 

 their vitality, by stimuli applied to themselves. Mechanical and chemical 

 influences, cold, heat, and electricity, produce this effect. They do not lose 

 their vitality immediately on the general death of the system, which must be 

 considered as taking place when the circulation ceases without a power of 

 renewal ; in cold-blooded animals it is retained much longer after this period 

 than in the higher Vertebrata, in some of which it disappears within an hour. 

 From experiments on the bodies of executed criminals, who were previously 

 in good health, Nysten ascertained that in the Human subject, the contractility 

 of the several muscular structures departs in the following time and order. 

 The left ventricle of the heart first ; the intestinal canal at the end of 45 or 55 

 minutes ; the urinary bladder nearly at the same time ; the right ventricle 

 after the lapse of an hour ; the oesophagus at the expiration of an hour and a 

 half; the iris a quarter of an hour later ; the muscles of Animal life somewhat 

 later ; and lastly, the auricles of the heart, especially the right, which in one 

 instance contracted under the influence of galvanism 16| hours after death. 

 The muscles of young animals generally retain their contractility for a longer 



* The distinctness between the two is remarkably shown in bodies infested with the 

 Trichina spiralis, which, whilst it profusely infests the foraier, is seldom or never found 

 in the latter; so that there is a definite line of demarkation, even in closely contiguous 

 parts, such as at the lower edge of the inferior constrictor of the pharynx. 



