10 PHYSIOLOGY CHAP. 



According to Griitzner (1883) each muscle contains rapidly 

 contracting and slowly contracting fibres, which cannot always be 

 distinguished by their colour. Speaking generally, he holds that 

 the latter, which are less excitable and less easily fatigued, are 

 richer in sarcoplasm, darker and thinner; the former, on the 

 contrary, are more excitable and more easily fatigued, less rich in 

 sarcoplasm, lighter and thicker. Easier (1904-5), in Griitzner's 

 laboratory, afterwards confirmed and extended these researches. 



Paukul (1904), who examined the forms of twitch from almost 

 every muscle of the rabbit, came to the conclusion that the 

 different modes of contraction depend on the arrangement of the 

 muscle fibrils and the intervening sarcoplasm ; those muscles in 

 which fibrils lie uniformly and are surrounded by little sarcoplasm 

 contract rapidly, while those in which the fibrils are arranged in 



FIG. 5. Influence of temperature on amplitude of muscular contraction. (A. D. Waller.) 1, con- 

 traction of normal gastrocnemius ; '2, of same muscle, slightly cooled ; 3, of same muscle, much 

 cooled. / 



A 1 



groups and separated by a large amount of sarcoplasm contract 

 more slowly. 



(b) Temperature, either higher or lower than the normal, has 

 a marked influence upon the course of the muscular contraction. 

 Cooling always lengthens the contraction, and raises its height 

 when the degree of cooling is moderated, but lowers it if more 

 marked (Fig. 5). Warming constantly accelerates contraction 

 and increases its height when moderate in degree, but lowers it 

 when more pronounced. Gad and Heymans found the maximum 

 height of contraction at 30 C. It is diminished as the tempera- 

 ture falls to 19 C, and subsequently rises again at C. 



Patrizi examined muscular contraction in the marmot, both 

 in the hibernating and in the waking state, which are, of course, 

 distinguished by great differences of temperature. He found that 

 contraction is about three times more rapid when the animal is 

 awake than in hibernation ; and determined the latent period and 

 duration of the different phases of the twitch, and the stimulation 

 frequency required to produce tetanus, in both these states, that is, 

 with both the high and the low body-temperature. 



