288 



DR. G. ELLIOT SMITH ON 



iucliuled in tlie pyi-iform lobe {lobus pyriformis anticns), is generally referred to as the 

 " tracfns olfactorlus." This confusion may be avoided if we restrict the term olfactory 

 tract to its literal meaning as the group of nerve-fibres lying on the surface of a cortical 

 area, Avhich. is the cephalic extension of the pyriform lobe. [To be strictly accurate we 

 should say that the lobiis pijriformis postictts is the greatly expanded caudal extension 

 of the lobtis 2^!/f'ifor7nis anticns, but as the name " pyriformis" is usually associated 

 exclusively with the former, I have spoken of extending it (the name) to the latter.] 

 I have deliberately avoided the use of the term " hippocanipal lobule," or any of 

 the many vai'iants of this term, because such expressions introduce a most undesirable 

 confusion with the true "hippocampus," a structure quite distinct from the pyriform 

 lobe, but one which in literature is frequently mistaken for it as a result of the 

 confusing nomenclature in common use. This is an interesting example of the 

 widespread misconception to which such loose nomenclature can lead in comparative 

 anatomy : for the student of the literatvxre x'elating to the fore-brain in Reptilia and 

 Dipnoi (more especially Burckhardt on Protopderiis) has had but too clear a demonstra- 

 tion of the utterly chaotic state of the morphology of the fore-brain which the confusion, 

 of pyriform lobe with hippocampus can produce. If we consider tlie base of the 

 hemisphere as a whole, it will be found to present a pyriform shape. It is broadest at 

 its posterior extremity, and contracts gradually as it extends forward, so that it passes 

 insensibly into the large rounded stalk of the huge olfactory bulb which caps the anterior 

 extremity of the heniispliere. 



The hidhns olfactorius is a large conical cap of grey substance of about the size and 

 shape of a Albert nut. The contour of the ventral surface is not unlike the conventional 

 heart-shape, with the apex pointing forward. This surface is indented by a deep 



Fis. 2. 



cerebellum 

 Bss. prima 



ped. olfact. 

 bulb. 9lfact.1 



i fiss. flocculi 



parafloco. dors. 



medulla oblong. 



lob. pyriform. ant. ' 



tract, olfact. 



tnbercul. olfact. 



Corp. geniculat. ant.;crus. : ,?°'^^, ■ parafiocc. veutr. 

 I cerebri area "arol. , *^ 



Corp. tegmenti flocculus 



geniculat. post. 



Left lutenil hurt'ace of biaiu of Uri/ctcio^m.s. .Xat. size. 



The cerebral hemisphere has been separated from the rest, by cutting the jmictiou of the optic tbahimus 

 and corpus striatum so as to expose the Literal aspect of the thalamic aud mid-brain. 



sagittal fissure which is placed nearer the lateral than the mesial border. This fissure 

 indents the whole thickness of the wall of the olfactory bulb, so that when we examine 



