102 DEVELOPMENT OF MUSCLE. 



existing fibres. Weissmanji and Ki'ihne describe in addition a 

 peculiar splitting of the primitive tubes in tlie direction of their 

 length. This phenomenon was studied ]n' Weissmami in the 

 muscles of the frog, bv Kvlme in those of rats and mice. The 

 latter observer describes a marked increase in the number of 

 nuclei and the quantity of finely-granular protoplasm at the 

 points where the nerves enter. Weissmann saw the nuclei 

 arranged in a row, dividing the contractile substance of the 

 muscular fibre into two parallel bands. Kiihne came across two 

 muscular fibres in a single tube of sarcolemma. All these are 

 facts which give us some sort of idea, though not a distinct pic- 

 ture, of the longitudinal splitting of the muscular fibre. Not a 

 word is dropped by either observer suggesting any after-produc- 

 tion of embryonic cells, destined for the additive formation of 

 new primitive tubes. In disease matters take a different course. 

 The repair of divided muscles by muscular tissue is indeed still 

 very doubtful ; beyond all doubt, however. Is the regeneration 

 of the muscular fibre in myositis typliosa, which we shall have to 

 consider more fully hereafter. But in this latter case the pheno- 

 mena are so complicated that we are unable to affirm w^ith cer- 

 tainty that the regeneration is brought about exclusively by the 

 mediation of embryonic cells. 



We can speak more confidently about such organs as are 

 made up of unstrlped muscle. During tlieir growth the cells 

 increase in number as well as in leno-th and thickness. Slns^le 

 fibres with forked extremities have often been met with in the 

 walls of the pregnant uterus.* Inasmuch, however, as no mul- 

 tiplication of nuclei, no double nuclei, have ever been detected 

 in these fibres, it remains very doubtful whether we are justified, 

 on the above data, in assuming a fissiparous multiplication of 

 the smooth muscular fibres. The doubtfulness of this hypothesis 

 is enhanced by a positive observation of KbllikiTs. He succeeded 

 in tracing the origin and development of the muscular fibre 

 through all its stages in one and the same specimen. (Cf. KoUiker, 

 " Gewebelehre," 4te Auflage, page 567.) The embryonic cells 

 required are furnished by the intermediate apparatus of nutrition, 

 and are probably leucocytes which have emigrated from the 

 vessels. 



* Moleschott and Piso in Moleschotfs *^Untersuclmngen," vi. 1-6. 



