78 MARION HINES 
fissura prima is the result of the separation of the olfactory 
lobe, or the anterior smell brain, on the medial side through a 
medial continuation of the lateral fissura rhinica (p. 76). This 
fissure does not extend to the lamina terminalis. It remains 
in the adult as the fissura parolfactoria posterior of the B. N. A. 
The posterior arched fissura or the fissura hippocampi is a reality 
because it contains a characteristic structure in no wise connected 
with postmortem changes. ‘The fissura arcuata accessoria lies 
above the hippocampal in His’ published models. He fails 
to state whether or not there is any characteristic histological 
structure present in its depth. 
Retzius (01, p. 92) says that, although the lateral hemisphere 
wall is smooth, there is a broad sagittally placed furrow or in- 
denture, in the medial wall forming a hillock, which butts into 
the ventricle. A year later (p. 66) he says the same in regard 
to the matter. 
Such is the history of the transitory fissuration in the human 
telencephalic vesicle. But what of lower animals? Only two 
workers have identified structures similar to the findings of 
Goldstein, Retzius, and His; they are Martin and Gronberg. 
Martin (94) was able to identify the anterior arched fissure 
in a transverse series of cat embryos, 1.3 cm. in length (p. 224). 
It appeared later than the fissura chorioidea (0.9 cm.). In the 
cat, the anterior arched fissure resembles the fissure pictured 
by His (pl. I, fig. 8,’90). The posterior arched fissure appears as 
a secondary arched fissure (2.2 em., p. 226). The union (at 
5 em.) of the anterior and posterior fissures with the ‘seitlichen 
Balkenfurche’ (i.e., the sulcus fimbrio-dentatus) he considers to 
be the future fissure of the corpus callosum (p. 242). This 
fissure maintains the same relationship to the pallial commissure 
as the sulcus corporis callosi of the rat (Johnston, ’13, fig. 59). 
The same sequence of fissuration was followed by Grénberg 
(01) in the brain of the hedgehog. The choroid fissure appears 
in the 1l-mm. embryo and the arched fissure in the 15-mm. 
In figure 54 the inner wall is evidently thickened and forms a 
slight bulging into the lumen of the ventricle. 
