3 i2 THE BIOLOGY OF THE FROG chap. 



result of shock effects, and that frogs carefully operated 

 upon and given time to recover, performed coordinated 

 jumping and swimming movements remarkably well. The 

 center for locomotion cannot, therefore, be located in the 

 optic lobes. Removal of the optic lobes was found by Loeser 

 to produce forced movements, an abnormal retention of 

 urine, and a slight loss of sight, but later these symptoms 

 gradually disappeared. Frogs with the brain removed as far 

 back as the medulla locomote normally, perform the croak- 

 ing reflex, breathe regularly, and show the usual compensatory 

 motions. 



The optic lobes exercise an inhibiting influence on the 

 reflex activity of the spinal cord. Removal of the optic 

 lobes results in an increased irritability of the cord, while 

 stimulation of the optic lobes may greatly check spinal 

 reflexes. If one optic lobe is stimulated, the spinal reflexes 

 on the opposite side of the body are inhibited, while those 

 on the same sides are not noticeably affected (Langendorff). 



The Cerebellum. — The cerebellum of the frog is so small 

 compared with that of most other vertebrates, that it would 

 not be expected to have an important function. Steiner 

 found that frogs from which the cerebellum had been 

 removed were apparently unaffected by the operation, and 

 other investigators have confirmed this conclusion. Goltz, 

 however, found that coordinated locomotion was disturbed 

 after extirpation of the cerebellum, but, as was admitted later, 

 somewhat more than the cerebellum alone was removed. 

 Recently, however, Loeser has arrived at results similar to 

 those of Goltz. After removal of the cerebellum, according 

 to Loeser, " the jumps became very unsteady and were 

 weakened in force, but not much reduced in rate. Most of 

 the time the frog lay stretched in contact with the floor 

 of the vessel and covered with moss. The unsteady and 



