Donaldson, Nervous System of the Frog. 327 



Weight of the brain. 



The brain, within the Hmits given below, was raised on a 

 narrow spatula, and the cranial nerves cut at their junction with 

 it. The pia was for the most part left adherent. The choroid 

 covering, the fossa rhomboidalis, and the hypophysis, were both 

 removed, however, before the weight was taken. 

 Weight of the spinal cord. 



The roots of all the spinal nerves were cut close to the 

 cord itself, and this, within the limits given below, still covered 

 with the pia, was then weighed. 

 Length of the Brain. 



With spring compasses the measurement was made from 

 the frontal end of the olfactory lobes to the caudal end of the 

 calamus. The olfactory bulbs and tracts were thus excluded. 



Length of the spinal cord. 



The cord was measured in the same manner as the brain. 

 The limits chosen were from the tip of the calamus to the point 

 of attachment of the dorsal roots of the tenth spinal nerve. 



The plane separating the brain from the cord thus fell a 

 small fraction of a millimeter cephalad to the point of emer- 

 gence of the first spinal nerve. 

 Condition of the frog. 



When the condition is noted as " dry " it means that the 

 frog was kept exposed to the air in a dry jar for twenty-four 

 hours previous to examination. 



In such cases the body-weight according to which the frog 

 is entered in the table, is that taken after the drying. The 

 " wet" body-weight would be higher. 



The cases marked " wet " are from frogs so placed that for 

 twenty-four hours previous to examination they could not get 

 out of the water. 



The cases which bear no indication were undetermined, 

 and although the proportion of water in them probably varies 

 in no small degree, they were from frogs so placed that they 

 could be in or out of water at will. 



That the "dry" frogs stand too low in the table owing 



