120 CARNEGIE INSTITUTION OF WASHINGTON. 



developed between the neuro-fibrillar net and the muscle-fibers forming 

 transverse plaques which form previous to and he within the sarcolemma 

 and apparently are comparable to the receptive substances of Langley 

 found in motor nerve-endings. In the later stages these plaques become 

 obscured by the thickening of the fibrillar net. Finally, in pigs 200 

 mm. long the entire spindle-mass becomes inclosed in a connective- 

 tissue sheath, such a spindle consisting of as manj^ as 15 fibers. It is 

 interesting to note that no degenerating muscle-fiber was found by this 

 investigator where the muscle was provided with a nerve-fiber. 



In previous experimental studies on the amphibian ear-vesicle Dr. 

 Streeter has investigated the factors concerned in the determination of 

 the posture of the ear-vesicle and the resultant membranous labyrinth. 

 It was shown that where the ear-vesicle is transplanted to another 

 specunen and intentionally placed in an abnormal posture there is a 

 subsequent spontaneous correction to normal posture and that the 

 resulting labyrinth bears normal relations to its environment. The 

 next step was to estimate the time at which this spontaneous rotation 

 of the ear-vesicle occurs. During the past year this has been fairly 

 well determined, so that the histological conditions under which the 

 phenomenon occurs can now be studied. 



Dr. Gilbert Horrax produced experimental degeneration of the ven- 

 tral an,d dorsal spino-cerebellar tracts by a lateral incision in the 

 thoracic region at the level of the sixth thoracic vertebra of the spinal 

 cord of the dog. Examination of the material prepared by the Marchi 

 method from three such experiments showed that there was an ascend- 

 ing degeneration on both sides of the cord, though more marked on the 

 operated side. The fibers could be traced from the dorsal tract to the 

 caudal half of the vermis and the adjacent medial portion of the lateral 

 hemispheres of the cerebellum; from the ventral tract the fibers could 

 be traced to the cephalic half of the vermis. Loss of muscle sense and 

 tone in both hind legs followed the operation, from which there was 

 complete recovery in 3 weeks. These results confirm the work of other 

 recent workers who have approached the problem in difterent ways. 



A volumetric study of the development of the parts of the brain is 

 being made by Dr. Streeter and his co-workers. The object in view is 

 to obtain a history of the volume gi'owth of the individual parts of the 

 brain, wdth the idea that a knowledge of their volume priority would 

 indicate in a general way the functional priority of these parts. By 

 the method of wax-plate reconstructions, enlarged models of the embr\'o 

 brains are made which can be separated into their chief component 

 j)arts. Since in a given model the wax is of a uniform composition the 

 relation by volume and b}^ weight of the different parts can be deter- 

 mined both as to each other and to the brain as a whole. The study 

 of one stage — the brain in a fetus of 156 mm. crown-rump measure- 

 ment — ^has been completed and pubhshed by Professor F. C. Dockeray. 

 Studies of other stages are well under wa3^ 



