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pyramidis"), which does not join the pyramid (middle lobe), but the 

 uvula (posterior lobe). The suprapyramidal fissure in this case joined 

 the parapyramidal fissures (the arrangement which occurs normally in 

 most Primates), so that the pyramid and the parapyramidal areas 

 were in uninterrupted continuity. Bradley described a similar ano- 

 maly in the brain of Lepus (op. cit. 9), but wrongly imagined it to 

 represent the normal mammalian arrangement. In a foetal brain of 

 Bos, I have seen a fissure, which develops within the pyramid, join 

 the parafloccular fissures (such as often happens in the smaller Ro- 

 dentia, Marsupialia and Chiroptera) ; but in addition to the copular 

 band passing to the pyramid there also was present in this particular 

 Ox's brain a second copular band connecting the paraflocculus and the 

 uvula. Such anomalies show that it is misleading to speak of the 

 paraflocculus as "belonging" to any particular part of the vermis, be- 

 cause the purely-mechanical factors of fissure -formation may produce 

 all sorts of fortuitous combinations of surface-areas 1 ). This is parti- 

 cularly well- exemplified in the case of the human brain, the normal 

 pattern of which differs from that of other mammals in this particular 

 region. 



In the brain of Man (as also in all Apes and most Lemurs) the 

 suprapyramidal fissure invariably becomes confluent with the para- 

 pyramidal fissures (Figs. 20 and 21). In all Primates the parapyra- 

 midal area becomes subdivided into two parts, which are known in 

 the human brain as the u lobus biventralis" and the "tonsilla" ("amyg- 

 dala") respectively. These are separated by a fissure, which I shall 

 call "posttonsillaris". In a large proportion of human brains the great 

 expansion of the alar parts of the middle lobe tends to push the para- 

 pyramidal area downward and it so happens that, for apparently me- 

 chanical reasons, the fissura secunda as it extends laterally (Fig. 1 d) 

 is prolonged into (instead of below) the parapyramidal area and fre- 

 quently (or even usually) becomes confluent with the posttonsillar 

 fissure (Fig. 20). Another factor, which comes into play in producing 

 this result, is the noteworthy increase in size of the tonsilla in the 

 human brain. Even in the Anthropoid Apes the tonsil is quite in- 

 significant in comparison with that of Man. 



Although this uninterrupted continuity of the uvula and the tonsil 

 (the most ventral subdivision of the paravermis) is the most common 

 arrangement in the human brain it often happens that there is no 



1) At the same time it shows that the term "copula pyramidis" cannot 

 be applied to all mammalian cerebella. 



