— 6o — 
Of the numerous papers on the invertebrate-nervous system, 
which have appeared in recent times, we will only refer to a few. 
The most remarkable work in the latest literature on this subject is 
Leydigs »Zelle und Gewebe« (1885) which has been already mentioned. 
There, he has modified, or to a certain extent changed, his previous 
view of the dotted substance. The fibrillar reticulation, which he and 
others have described, becomes nothing but a spongy net-work of 
supporting substance, spongioplasm, in the cavities of which the homo- 
geneous, really nervous substance, hyaloplasm, is diffused; the gang- 
lion cells as well as the nerve-tubes consist of the same substance. 
The nerve-tubes originate in this way: the spongioplasm, which in the 
central mass is quite diffusively arranged, unites and forms longitudinal 
fibres and sheaths which envelope the hyaloplasm like tubes ; an}^ 
isolation of nerve-tubes or fibrillæ in the central dotted substance 
can thus, as a rule, not arise. It will be seen that this is a rather 
radical revolution in the views of most histologists. To a certain 
extent, in respect of the supporting substance of the central mass, 
it certainly reminds somewhat of Claus ; in all other respects, however, 
Leydig holds a view quite different from that of the author named. 
Pruvots view (1885) of the dotted substance or »matiére 
ponctuée« seems to be of a somewhat peculiar kind; he has not, 
indeed, succeeded in finding its real nature. In the brain, he de- 
scribes it in the following way (1. c. p. 232): »C'est une matiére 
homogene, refractaire aux colorations, offrant un fin pointillé qu' un 
grossissement suffisant permet de resoudre en petites granulations 
reguliérement espacées et traversée seulement par quelques rares 
fibres anastomosées qui proviennent de la substance corticale.« 
What these » granulations « and » rares fibres anastomosées « really 
are in Pruvots opinion, I dare not say, I think it is evident that his 
powers of magnification have not been sufficiently high. 
In his »conclusions générale« (1. c. p. 323) he gives the follow- 
ing summary of his researches on this subject: »p]n effet tous les 
éléments fibrillaires nerveux (prolongements des cellules, fibres des 
nerfs et des connectifs) traversent sans modifications la substance 
corticale, mais au niveau de la substance méduUaire se fragm.entent, 
se résolvent en petites granulations d'abord tres rapprochées et dis- 
posées en séries linéaires, qui s'espacent peu å peu et se perdent 
au milieu des granulations voisines pour constituer la matiére ponctuée. 
Cellesi est done un intermediaire entre la cellule et la fibre, entre 
félément central et félément conducteur . . . .« As will be seen, 
this is no very distinct description; his idea of the dotted substance 
