Junk 17, 1898.] 



SCIENCE. 



815 



The search for the structural evidence for 

 such coordination cannot be said to have 

 been very successful, though the statements 

 of numerous observers respecting ' inter- 

 cellular bridges ' and other means of com- 

 munication have served to keep alive a 

 spirit of expectancy. It is the purpose of 

 this paper to offer an illustration of a struc- 

 tural basis for vital or somatic coordination 

 which seems, so far as a cursory glance at 

 the literature enables me to judge, not to 

 have received any adequate interpretation. 

 It may be said in advance that the prevail- 

 ing idea that the body is made up of close 

 ranks of cells set immovablj^ in tissue as 

 stones are cemented in a wall is applicable 

 to comparatively few parts of the body. 

 Any one who has observed the structure of 

 the embryonic bodj', say of a vertebrate, 

 must have been struck with the fact that 

 the interspaces between the embryonic tis- 

 sue are wonderfully permeable to the in- 

 vasion of proliferating and migrating cells 

 of all kinds, so that the developing nerve, 

 for example, has no difficulty in reaching 

 its destination as it grows by progressive 

 proliferations at its tip. In the adult the 

 brain offers an illustration of a similar per- 

 meability, and the effectiveness of the organ 

 depends, in no small degree, upon the fact 

 that nu1;riment-bearing cells make their 

 way with great freedom among the neural 

 elements. There can be no doubt that the 

 brain cells are undergoing constant renewal, 

 and it is now admitted that the degenera- 

 tions observed in the cortex of paralytics 

 cau be duplicated in kind in the relatively 

 normal brain. 



Our own present illustrations are derived 

 from the preparations of the skin of the 

 axolotl and the horned toad, two subjects 

 sufficiently different from each other to war- 

 rant us in believing that structures found 

 in both are present quite generally, a least 

 within the two classes they represent. The 

 skin of the Amphibia has been so exten- 



sively studied that it may appear incredi- 

 ble that conspicuous structures should have 

 escaped notice, but even should the details 

 not prove entirely new the illustration is an 

 apt one for my present purpose.* 



tterves 

 FlQ. 1. Section through skin of axolotl hardened 

 in Merkel solution J, stained with picrocarmine and 

 hoematoxylin. Nerve fibres, passing through the 

 corium, enter a plexus demonstrable by methyleu 

 blue, and Don-medullated fibres ascend to attach 

 themselves to the naked intercellular protoblasts 

 which support the coarse reticulum. One Leydig 

 cell is not cut by the section and over its surface the 

 meshes are entire ; in other cases only the cut ends 

 are shown by focusing at different depths. 



It happened that in the search for a his- 

 tological method for the study of the cyto- 

 plasm various modifications of the chromic 

 and osmic acid fixers were employed, and it 

 was noticed that certain combinations of 

 chrom-acetic and platinic chloride, when di- 

 luted with alcohol, gave remarkably fine 

 fixation of protoplasmic structures without 

 impairing their susceptibility to stains to 

 the extent that osmic acid preparation no- 

 toriously does. After-treatment with hse- 

 matoxylin and either fuchsin, or, still better, 

 picrocarmine gave exceedingly distinct con- 

 trast stains. The protoplasmic structures 



*They have been seen, as indicated beyond, but 

 wrongly interpreted. 



