CONARIUM AND HYPOPHYSIS. 415 



of development) as completely circumscribed, usually ~by nervous 

 tissue, always by membranes. 



This idea is more or less distinctly enunciated, upon various grounds and respecting 

 various animals, by the following- writers : Foster and Langley (A, 224); Balfour (A, 364); 

 Todd (A, 634); Mihalkovics (A, 115); Duval (2, 33); Quain (A, II, 546); Hadlich (!) 

 Lowe (A) : Mivart (B, 266) ; and probably others. 



1084. The Conarial Tube. The above statement respecting the complete circumscrip- 

 tion of the creliae excluded the earlier embryonic stages on account of the views of Gotte 

 (A). According to this observer, as briefly stated by Balfour (A, 356), the conarium is the 

 remnant of the canal by which, as is commonly believed for Vertebrates in general, the cavity 

 of the embryo myelencephalon communicates with the ectal surface of the head. Accord- 

 ing to Stieda, as stated by Balfour (A, 357), a part of the conarial tract persists upon the 

 outside of the cranium with some Amphibia, and the corresponding orifice of the cranium 

 is identified as the parietal foramen of some fossil Reptiles by Owen (1). The entire 

 *' conario-hypophysial tract," as it is termed by Owen, has great morphological interest, 

 but for our present purposes it seems best to omit any detailed account of the various 

 views, and to refer only to the generally accepted opinion as to the primitive origin of the 

 hypophysis from the alimentary canal. (Owen, 1 ; Balfour, A, II, 358 ; Quain, A, II, 735 ; 

 Foster and Balfour, A, 91 ; Parker and Bettany, A, 10 ; Mihalkovics, A, 83). 



STUDY OF THE AMPHIBIAN BRAIN. 



1085. Obtaining the Animals. Directions for procuring frogs 

 and Menobranchi and caring for them will be given in the Appen- 

 dix. Large examples are to be preferred for the study of the brain, 

 and they should be obtained alive or freshly killed. 



1086. Killing. Place the animal in a jar or covered vessel of 

 water, and pour off any water in excess of what is needed to simply 

 submerge it. 



Pour in a little chloroform, not more than 5 cc. ; it will sink to 

 the bottom as oily looking drops. The movements of the animal 

 will usually diffuse it more or less, and the vessel may be shaken if 

 necessary. Death will ensue in 10-30 minutes. 



If ether is used, it will float upon the top of the water, the ves- 

 sel must be shaken, a longer time is required, and the animal is 

 more likely to revive unless the subsequent operations are done 

 without delay. 



If no anaesthetic is at hand, decapitation may be performed with 

 the bone scissors by cutting caudad from each angle of the mouth 

 to the caudal margin of the brachium in the frog and the caudal 

 gill in Menobranchus, and then cutting transversely so as to sepa- 

 rate the cranium and maxilla, with the first two or three vertebrae, 

 from the mandible and the rest of the body. This should be first 



