Connective Tissue, Nerve, and Muscle. 529 



situated directly under and apparently in contact with it ; and the nu- 

 merous foramina seen in the cylindrical rod left by the potash solution, 

 when the membrane has been loosened from it, are probably the points 

 where the elastic fibres penetrate. 



A muscular fibre is thus composed of a number of bundles resembling 

 those of tendon, arranged parallel to each other, each bundle giving 

 shelter to a number of fibrillae, and separated from the neighbouring bundles 

 by a space lined with flat cells. In the larger spaces lie branched cells, 

 and in the smaller the projecting processes of the elastic fibres given out 

 by the latter. 



The large holes I have described in the elastic sheath afford passage to 

 the nerves. When these have been traced, it is reasonable to infer that, 

 here as well as elsewhere, they will be found to follow the lymph-channels. 

 These holes not only permit the passage of nerves, but allow free com- 

 munication between the lymphatic spaces within the fibre and those 

 between the perimysium and the sarcolemma. 



The abundance of gelatinous substance in a muscular fibre accounts 

 for the phenomenon known as transverse cleavage, which is produced by 

 the action of very diluted hydrochloric acid. I regard it as essentially 

 equivalent to the effect produced in tendon when by similar treatment a 

 bundle divides transversely into the flat plates known as the " Donde- 

 rische Bander," after the distinguished histologist who first described 

 them. . 



To sum up these views regarding the structure of muscle in a few 

 words, it might be said that a muscular fibre is a fasciculus of tendon in 

 the bundles of which the primitive fibrillse are imbedded longitudinally. 



The small spaces at the points of junction of flat cells which colour 

 deeply in silver, and to which allusion has been made by histologists, are 

 seen in all tissues. They are always present when the colouring has been 

 intense, and should, I believe, be regarded as playing an important part in 

 the mechanism of the lymphatic system. They are especially well defined 

 in the rete Malpighi of the frog, where it would be impossible to regard 

 them as artefacts. 



It is evident from the various anatomical facts above detailed, that the 

 tissues may be said to be in an almost unbroken continuity with the 

 lymph-system*. When a blood-corpuscle escapes from a capillary it is 

 into the cell-lined spaces of this system that it directly passes, and there 

 is manifestly no obstacle to the passage of the contents of the lymph- 

 channel into the blood other than that formed by the wall of the capil- 

 laries, which alone separates the fluids of the lymphatic and vascular 

 systems. "We know that white blood-corpuscles can make their way 



* In this connexion I quote from Ranvier's essay (I. c. p. 485) the following sen- 

 tence : " L'existence, dans le tissu cellulaire sous-cutane", de ces cellules plates, dis- 

 posees a la surface des faisceaux, ne nous suggere-t-elle pas 1'idee de voir dans le 

 tissu conjonctif un vaste espace cloisonne", analogue aux cayites sereuses ?" 



