822 SUMMARY OF CURRENT RESEARCHES RELATING TO 



of the structures described by Margo * under the name of " Sarco- 

 plastin " ; there are lines or chains of muscle-corpuscles, united by 

 the protoplasm net, and derived by proliferation from the corpuscles 

 of the original fibres ; the sarcoplast gradually separates from the 

 parent fibre, undergoing muscular differentiation meanwhile, and also 

 becoming connected with the nerve. The growth of the fibre is 

 initiated by a multiplication of the corpuscles ; the sarcolemma is not 

 present at first, but appears later, being probably formed by the fused 

 cell-membranes of the corpuscles, to which appears to be added a coat 

 of connective tissue, and also around the motor plate between the two 

 sarcolemmic coats, an extension of Henle's sheath of the nerve. 



The motor nerve-plates are formed as follows. When the sarco- 

 plast begins to change to muscle, the nerve grows towards it until the 

 two meet and unite. In lizards only a single nerve-fibre, in the frog 

 and mouse several together, thus approach the future muscle. At the 

 point of contact the muscle-corpuscles change, so that an accumula- 

 tion of protoplasm and a proliferation of nuclei occur there. These 

 accumulations were first described by Kiihne under the name of 

 " Muskelspiudeln," f and are mentioned by many subsequent writers. 

 Bremer now shows that they are young " end-plates." Into these the 

 ramifications of the nerve penetrate, after the medullary sheath has 

 been lost. The details of the process, of course, vary in different 

 animals, as do also the final forms of the motor plates. 



Besides the motor terminations there are others which the author 

 believes to be probably those of the sensory nerves. The fibres 

 running to them are either small and meduUated or naked, and end 

 in ramifications upon the muscle, without any conspicuous collection 

 of nuclei and protoplasm at the place of junction. The smaller nerve 

 endings occur on the same fibres with the motor plates, and probably 

 both exist on every fibre. The smaller endings Bremer designates as 

 " Enddolden," in contradistinction to the " Endplatten." (Sachs's 

 paper on the sensory nerves of muscles is not cited by Bremer.) 



Hensen has advanced the view that the connection between the 

 nerves and the peripheral cells exists from the first in the embryo, 

 and that, as the cells divide, so do the nerves. Bremer's observations 

 show that with muscles this is not the case. Moreover, Kleinenberg's 

 theory of the evolution of muscle and nerve must be at least 

 modified, if not set aside. That the union of the nerve-filament 

 with the peripheral organ is secondary is shown also by His. 



Cell Theory.l — P. Geddes, in ' A Theory of the Life-history of 

 the Cell,' says, " Our current conceptions of the groups of the Pro- 

 tozoa are apt to be based upon their most prominent and permanent 

 characters only. One thinks of an infusorian as a ciliated or flagellated 

 organism of permanent form, of a radiolarian as a highly differentiated 

 rhizopod, with two layers of protoplasm, a gelatinous envelope, and a 

 siliceous skeleton, while in the description of a Heliozoon special atten- 



* SK. Akad. Wiss. Wien. xxxvi. p. 229. 



t Virchow's Arch. f. Path. Anat., 1863, p. 116. 



X Zool. Anzeig., vi. (1883) pp. 440-5. 



