Shki.don, Rrtiit/oiis to (^liruiicnl Stiiim/i. 293 



blood vessels of the roof of the mouth, as this leads to serious blcediug. 

 The loeatiou of the vessels to be avoided is shown in the dissection. 

 The fishes seemed to suffer no ill effect from this o})eration and would 

 live for some weeks thereafter. The profundus and superficialis 

 nerves were cut by means of ;in incision into the orl)it at the caudal 

 margin of the eye l)alb 



After section of the olfactory crura, stimulation of the nostrils 

 causes the same reactions as were obtained for normal fishes. It is, 

 therefore, evident that these reactions are not due to stimulation of 

 the olfactory nerve. When the four rami of the trigeminal are cut 

 and the olfactory left intact, no reactions are secured. This shows 

 clearly that the reactions obtained are due to the nerves of general 

 sensation. The associated nerves of the lateralis system have been 

 proved to be insensitive to chemical stimulation. The following 

 nerves were next cut without destroying the reactions ; the ophthal- 

 micus sujDerficialis, the ophthalmicus profundus and the oph. sup. and 

 oph. prof, together. When the nuixillaris-niandibularis trunk is cut, 

 however, all reactions cease. When normal fishes are taken, this 

 trunk cut on one side and not on the other, stimulation of the nostril 

 on the operated side calls forth no responses, while the nostril on the 

 normal side is as sensitive as before. As the mandibularis nerve goes 

 to the lower jaw excdusively, it is evident that the sensitiveness of the 

 nostrils to the chemical stimuli used is due to the maxillaris nerve. 

 These experiments also show that the nostrils in selachians are inner- 

 vated by the trigeminal nerve, as is the case in most other vertebrates. 



Some odorous substances were also used in the nostrils although 

 without results so far as the sense of smell is concerned. The sub- 

 stances used were the oils of cloves, pennyroyal, thyme and aniline 

 oil. A few cc. of the oil were placed in a 200 cc. flask of distilled 

 water and shaken violently. After a day or so most of the oil would 

 collect while the remainder remained in suspension in the water in 

 the form of small drops. This water was drawn off and called a sat- 

 urated solution. ISTormal fishes reacted very quickly when this solu- 

 tion is applied to the nostrils. When the olfactory crura are cut the 

 nostrils remain as sensitive as before. To clove oil, for instance, both 

 normal and operated fishes are sensitive to a solution of about 1/100 



