219 



the parietalia, having no support, fall downward toward the occipital 

 and the membrane between the two bones becomes thrown into a fold 

 (x), which notches the neopallium. From this it seems probable that 

 BiscHOFP's "Fiss. perpend, ext." is merely a mechanically produced 

 post-mortem furrow. If the head of a 5th or 6th month foetus is 

 carefully supported during the fixing and hardening process, I believe 

 that no such furrow will be found. 



Neopallium 



Fig. 2. Part of a horizontal section (of another foetus) to show the relation of 

 the furrow a to the ridge of membrane, .?;, which intervenes between the parietal 

 {os. par.) and occipital (os. occ.) bones. Enlarged. 



In the beautiful series of Tafeln in Gustaf Retzius' "Das 

 Menschenhirn" it will be seen that in most of the best -preserved 

 foetuses of the 5th and 6th months this "fissure" is absent. 



In one of my specimens a true sulcus was found alongside the 

 post-mortem furrow, but comparison with the figures in the memoirs 

 quoted above leaves no doubt that it is the latter which is called 

 "Fiss. perpend, ext.". 



Although Wilder records the fact that his "larabdoidal fissure" 

 (which, he says, is apparently identical with that called by Cun- 

 ningham "external calcarine" and "external perpendicular") underHes 

 and is in "distinct collocation" with the lambdoid suture "in foetuses 

 between the 3rd and 7th months" (op. cit., p. 186), he does not suggest 

 that there may be a direct causal relationship between the "fissure" 

 and the suture. 



At the same period of foetal life a furrow is often produced in 

 a similar manner by the membrane in the coronal suture (Fig. 1, ß). 

 Concerning this Cunningham has said: "I have been greatly puzzled 

 to account for the presence of a long deep furrow, which is occasio- 



