WILLIAMS : PHENOMENA OF MUSCLE-CONTRACTION. 5 1 



is also used up, as has been shown by Dr. Barfurth,^^ in an 

 inverse proportion to their activity, and this substance I have 

 attempted to show in a previous communication ^ '^ is, in them, 

 as in vertebrates, appHed to the development of muscle-energy 

 by oxidation, and, probably, derived from the carbohydrates 

 (starches) and, in a less degree, the proteids (vegetable albu- 

 men, vegetable fibrin, gliadin, &c.) of the food-stuffs. Accord- 

 ing to W. Beidermann ^ * the adductor muscles of Anodon 

 retain their irritability for several days when kept in the blood 

 of that bivalve. And, in conclusion, with regard to some one 

 or two very interesting points in the physiology of muscle- 

 contraction in the mollusca which are unique in the animal 

 kingdom. For these we must thank, in great part, Simroth, ^ ° 

 to whom, indeed, must be given the palm for original work and 

 observation on that group of living beings over which I hope 

 all the readers of this journal are enthusiastic. If the under 

 surface of the foot of a snail be watched as it crawls along a 

 glass plate it will be observed that a wave passes along the 

 foot while the animal bends from side to side. These two 

 movements are accomplished by two different sets of fibres 

 and by two different modes. The former set run longitudin- 

 ally in the substance of the foot (extensile fibres), the latter 

 in an oblique direction (contractile fibres). The extensile 

 fibres are the active agents in locomotion and cause an exten- 

 sion of the foot; the contractile fibres cause a shortening of the 



*^ "Vergleichend-histochemische Untersuchungen iiber das Glycogen." 

 Arch. Mikr, Anat., xxv, pp. 259 — 404. 



'^ "On the Meaning of the Glycogenic Function in the Mollusca." 



'* "Ueber die electrische Erregung der Schliessmuskel von Anodonta," 

 S. B. Ak., Wien, xci., pp. 29 — 96. 



'^ "Die Thatigheit der willkiirlichen Muskulatur unserer landsch- 

 necken." Z. Wiss, Zool., xxx, suppl. vol., pp. 166 — 224. 



"Die Bewegung unserer landschnecken. " Op. at., xxxii., pp. 

 284—322. 



"Ueber die Bewegung und das Bewegungsorgan von Cyclosto?na 

 elegans, und der einheimischen Schnecken uberhaupt." Oj>. cit., xxxvi, 

 pp. I — 67. Z. ges Naturw. (2) v, pp. 500—504. 



