822 OP THE STRUCTURE AND FUNCTIONS OF MUSCULAR TISSUE. 



ordinary striated muscular tissue, probably depending upon the peculiar 

 arrangement of its fibres, whereby the contraction of one set gives a mechan- 

 ical stimulation to others ; for the muscular substance of a large part of the 

 organ is thrown into rapid and energetic contraction by a stimulus applied 

 at any one point, and this contraction is speedily followed by relaxation, 

 which is again succeeded by a number of alternating contractions and relax- 

 ations. 1 Each contraction, however, has been shown to be equivalent to a 

 single shock in an ordinary striated muscle ( 667). On the other hand, if 

 we apply a similar irritation to a portion of non-striated fibre, as that of the 

 Intestinal Canal, the fasciculus which is stimulated will contract less sud- 

 denly, but ultimately to a greater amount ; its relaxation will be less speedy, 

 and before it takes place, other fasciculi in the neighborhood begin to con- 

 tract; their contraction propagates itself to others, and so on. In this man- 

 ner consecutive contractions and relaxations may be produced through a con- 

 siderable part of the canal by a single prick with a scalpel. Again, in the 

 muscular structure of the Bladder and Uterus (when the latter is fully 

 developed), direct irritation excites immediate and powerful contractions, 

 which extend beyond the fasciculus actually irritated, and produce a great 

 degree of shortening ; but they do not alternate in the healthy state with any 

 rapid and decided elongation. Similar phenomena may be observed on irri- 

 tation of the smaller arteries. In order to obtain the full contraction of a 

 muscle by irritation applied to the nerves, it is requisite that the stimulus 

 should be applied for a certain length of time ; thus Budge 2 found that when 

 an electric current was passed through the cervical region of the spinal cord 

 of a rabbit for the space of half a second, the pupil dilated about one-sixth 

 of an inch ; but on continuing the application for three seconds, dilatation 

 occurred to the extent of nearly one-third of an inch. In all cases relaxa- 

 tion speedily alternates with contraction, unless the operation of the stimulus 

 be continued as when an electric current is propagated without intermis- 

 sion along the nerve-trunks in which case the contraction lasts as long as 

 'the stimulus is continuously applied, but ceases as soon as it is withdrawn. 

 The singular "inhibitory" effects produced by irritation of some nerves, as 

 the pneumogastric and splanchnic, have already ( 244, 96) been alluded 

 to ; but further experiments are still required before it can be admitted that 

 any nerve can really transmit a " stimulus to relaxation " on the part of the 

 muscle to which it is distributed. The general fact that relaxation alter- 

 nates with contraction at no long intervals is most evident in the rhythmical 

 movements of the Heart, 3 and in the peristaltic action of the Intestinal 

 Canal ; since in these parts the whole or a large proportion of the fibres seem 



1 Ray Lanke.ster (Pfluger's Archiv, 1871, p. 315) has shown that the muscular tis- 

 sue of the Heart is characterized by containing hsemoglobin. 



1 Physiologic, 1862, p. 650. 



3 Some curious rhythmical movements have been observed by M. Brown-Sequard 

 (Gaz. Med., 1849) in the diaphragm, in the intercostal^, and in some of the muscles 

 of locomotion, both after death and after section of their nerves during life. These 

 movements could not be in any way dependent upon reflex action, because they took 

 place when the muscles were completely cut off from the nervous centres, sometimes 

 to the number of from 5 to 20 in a minute, and for as long as a quarter of an hour 

 after death ; and occasionally recurred in living animals for many months afterwards, 

 especially when the respiration was impeded and the circulation hurried. Of a simi- 

 lar nature are the vibratory movements of the muscles of the tongue witnessed by 

 Schin" after section of the Hyoglossals (Physiologic, 1859, p. 177) ; and we may per- 

 hapi- ivi'.T to the same category the trembling movements of the hands and head in 

 old age, in certain forms of paralysis, and in habitual drunkards and smokers. All 

 these cases furnish evidence of a tendency to rhythmical movements in the muscles 

 themselves, altogether independent of the excitement to action which they receive 

 through the nervous system. 



