PEEFACE. xiii 



of investigations carried out by his pupil Miklucho-Maclay (" Vergleich. 

 Neurologic der Wirbelthiere," 1870), modified the current nomenclature of the 

 lobes of the Fish's brain, so that the large bispherical part, which was usually 

 considered as the mesencephalon in the Teleostei and Selachii, was assigned 

 to the thalamencephalon — or second of the five cerebral segments — whilst 

 the unpaired large projecting lobe, usually considered as the metencephalon 

 (cerebellum, fourth segment), was identified with the mesencephalon of higher 

 Vertebrates, and the cerebellum was considered as being represented by a 

 small transverse plate, often overlapped by the folded mesencephalon, and 

 usually of no larger size than the piece similarly identified in the frog. In 

 the present edition Professor Gegenbaur has modified this system of nomen- 

 clature, and has returned to the older and usually accepted method of 

 naming the parts of the Fish's braiii. Thus in Fig. 281, d marks the two 

 spherical masses which were in former editions assigned to thalamencephalon, 

 and are now, as is usual with other anatomists, designated mesencephalon, 

 the expansion between them and g being the reduced area of the thalamen- 

 cephalon. The letter h is now referred to as metencephalon (cerebellum) : 

 this was previously referred to as mesencephalon ; the myelencephalon 

 prosencephalon, and rhinencephala retain their names, which had not been 

 affected by Maclay's system. 



Whilst Professor Gegenbaur has returned to the usual system of naming 

 these parts, he still considers that the facts on which Maclay's nomenclature 

 was based possibly point to homologies other than those indicated by the 

 names ; so that the Fish's cerebellum does not necessarily agree with that of 

 higher Vertebrata. He remarks : " The mesencephalon is usually considered 

 as being confluent with the thalamencephalon in Selachians ; and a part 

 which really represents it, so far at least as relations of position are con- 

 cerned, is customarily called by the name 'cerebellum.' " 



In translating the German terms, Vorderhirn, Zwischenhu-n, Mittelhirn, 

 Hinterhirn, and Nachirn, I have adopted Professor Huxley's equivalents, 

 namely Prosencephalon, Thalamencephalon, Mesencephalon, Metencephalon, 

 and Myelencephalon. In the edition of Quain and Sharpey's Anatomy, 

 published in 1867, a similar but not identical series of terms was suggested. 

 For the "primitivenHirnschlitz," — the early strongly-marked sinking in of the 

 cerebral roof which separates the prosencephalon from the thalamencephalon 

 - — we have no special term in use ; " primitive cerebral cleft " is the transla- 

 tion which has been adopted. 



It is worth Avhile pointing out to the student, in connection with this 

 subject, and in fact in relation to the whole of the chapter on the Vertebrata, 

 that Professor Gegenbaur assumes some small amount of familiarity on the 

 part of the reader with descriptive human anatomy ; reference to a manual 

 treating of this subject, on the part of the student who has not previously 

 mastered it, is indispensable. 



Nomenclature of the Parts of the Digestive Tract. — The transla- 

 tion in the present Avork of the simple word "Darm," and its compounds 



