334 Transitory Fissures of the Human Cerebrum 
brain of an embryo three months old. Further observation by Hoch- 
stetter (1898) shows that they are not present in the fresh brain. Hoch- 
stetter examined the brains of two very fresh human embryos and in 
neither of them was there a trace of a transitory fissure. In other speci- 
mens which were well preserved the transitory fissures were only slightly 
marked, or were not present at all. The observations of Hochstetter are 
confirmed by Retzius, who had an opportunity to examine the fresh brain 
of an embryo of the third month. The membranous skull was removed 
and the specimen hardened in Zenker’s solution. After this treatment, 
it was found that the lateral and mesial surfaces of the brain were per- 
fectly smooth with the exception of a shght depression on the mesial side. 
It appears then that when the brains of fresh embryos of the third 
and fourth months are examined no transitory fissures are found. 
Furthermore, when fresh specimens are carefully hardened the trans- 
itory fissures are insignificant and not numerous, or are not present 
at all. 
About five years ago I noticed that the cerebral vesicles of human 
embryos hardened in formalin are entirely different from those hardened 
in alcohol. Not only are the vesicles perfect in form with walls in 
apposition to the membranes of the skull, but the arrangement of the 
cells is definite and clear. Specimens hardened in alcohol are some- 
times folded and usually macerated, the degree of maceration always 
being far in excess of that of the rest of the body. 
The recent publication of Retzius has induced me to tabulate the 
condition of the brains in my embryological collection to determine the 
frequency and degree of transitory fissures in brains hardened in formalin 
as well as in those hardened in alcohol. The table which I have con- 
structed records the condition of the brains in over fifty specimens. There 
are about a dozen excellent formalin specimens in the collection not 
included in the table, for they have not been sectioned and I am un- 
willing to injure them before they are cut into serial sections. It appears 
to me that these specimens recorded in the ‘table, together with the ob- 
servations of Hochstetter and of Retzius, set the transitory fissures 
aside as artificial products of the effect of weak alcohol upon the brain. 
The appended table gives the numbers, the length and the condition 
of the cerebral vesicles of embryos in my collection in which there are 
any data relating to the transitory fissures. The specimens have been 
grouped in months, using for this purpose a rule which has been pub- 
lished recently.” According to this rule the age of an embryo in days 
2? Mall, Johns Hopkins Hospital Bulletin, 1903. 
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