250 THE HEART, BY F. SCHWEIGGER-SEIDEL. 



fissures, which may be followed for some distance, both in 

 regard to length and depth. These fissures, to which Henle 

 has drawn attention, are in my opinion deserving of particular 

 notice. I find that they are lined by a very delicate mem- 

 brane, composed of flat cells, the contour lines of which, after 

 treatment with nitrate of silver, appear in the form of a black 

 pattern. Moreover, it is possible to raise up and isolate this 

 membrane after short maceration, which has confirmed me in 

 the opinion that many observers have considered it to repre- 

 sent the sarcolemma. The fissures, in fact, occur in the con- 

 nective tissue, as may be seen at their angles, and have in 

 rabbits, where, I think, they can best be seen, a length of from 

 0*06 to 0.25 millimeters. We shall return, however, to this 

 subject hereafter. 



The arrangement of the muscular bands in the wall of the 

 heart the so-called lamination of the cardiac musculature 

 cannot be fully treated of in this work, since it possesses no 

 histological interest. The careful investigations of C. Ludwig, 

 Pettigrew, Winkler, and others, have, however, shown how 

 complex these arrangements are ; and, according to Henle, in 

 addition to all these there must still be added the varieties 

 due to individual differences. The results of accurate exami- 

 nation seem to show that the musculature of the auricles, 

 speaking generally, is divisible into two layers, arranged at 

 right angles to each other, of which the external is circular, 

 but in the case of the ventricles the arrangement of the fibres 

 cannot be described in so simple a manner. We must pro- 

 bably seek for the immediate cause of the spiral arrangement 

 of the muscular bands that here exist in the history of its de- 

 velopment, as it is well known that at an early period the 

 cardiac tube forms not only a loop, but a spiral curve, through 

 which necessarily a deviation in the course of both the longi- 

 tudinal and transverse fibres will be occasioned. Sections 

 made through the wall of the ventricle, in a direction perpen- 

 dicular to the surface and parallel to the longitudinal axis, 

 exhibit, both externally and internally, longitudinally running 

 bands, whilst the median portion presents transverse sections 

 of the fibres ; consequently we can here, though only quite 

 generally, distinguish the two chief directions they pursue. 



