1 82 Journal of Comparative Neurology and Psychology. 



probable injury at time of transplantation, a pair of limbs developed out of each 

 transplanted bud, one by direct development and one by a process of budding or 

 super-regeneration.^ There were thus usually present in each specimen four distinct 

 kinds of transplanted limbs, v^^hich may be termed primary and accessory normal, 

 and primary and accessory nerveless. 



The specimens were preserved from four to six weeks after the operation. 

 Examination of serial sections shows that all four of the types of limb may, and in 

 fact usually do acquire nerves of normal structure and arrangement, and that these 

 nerves are always connected with the nerves of the host. In a typical specimen, in 

 which all four transplanted legs contained nerves, the primary nerveless limb had a 

 practically complete peripheral nervous system, derived from the sixth, seventh 

 and eighth spinal nerves, i.e., largely from nerves which normally do not enter 

 the limb. In the accessory limbs of both sides the larger nerve trunks and some of 

 the smaller branches were present, though a number of the branches, especially in 

 the distal part of the limb, could not be found. All this is contrary to the observa- 

 tions of Braus, who found nerves only in the primary normal transplanted limbs. 

 The difference in the results is due no doubt in a large measure to the fact that 

 Braus did not keep his specimens alive sufficiently long after the operation. 



The experiments cannot possibly be interpreted, as Braus interprets his, in 

 accordance with Hensen's theory of the development of the nerve paths. On the 

 contrary, when we consider them in connection with my former experiments' we 

 cannot but conclude that the nerves do actually grow from the host into the trans- 

 planted part, and further, that in so growing they are guided to the proper place by 

 the peripheral organs themselves, for, it must be remembered, the nerves of the 

 the transplanted limb except the n. cruralis are not derived from the same seg- 

 mental trunks as the corresponding ones of the normal limb, and therefore the 

 mode of branching cannot in any way have been predetermined in the nerves 

 themselves. 



A Model of the Medullated Fiber Paths in the Thalamus of a New-born Brain. 



By Florence R. Sabin, Anatomical Laboratory, Johns Hopkins University. 



The model is a reconstruction by the Born method of the fiber tracts of the 

 tha'amus that are medullated at birth and shows their relation to the cortex and 

 to (he brain stem. In the pons, the medial lemniscus is shown as a band of fibers 

 that separates the nuclei pontis from the tegmental part. On entering the mid- 

 brain, the lemniscus begins to curve lateralward on account of the red nucleus. 

 Just caudal to the red nucleus, the lemniscus gives off a small bundle of fibers to 

 the substantia nigra. The main bundle of the lemniscus passes beyond the red 

 nucleus on the way to higher centers, and divides into a ventral and a dorsal seg- 

 ment. The ventral segment is Forel's Feld H, the dorsal his Bath. The ventral 

 segment gives off a small bundle to thehypothalmic nucleus of LuY, similar to the 

 bundle given off to the substantia nigra; a second larger mass of fibers curves into 

 the hypothalmic region and enters the globus pallidus of the lenticular nucleus. 

 The rest of the ventral segment passes to the ventro-lateral nucleus of the thalamus 



D. Barfurth, Arch. f. Enlzvjcke/ungsmecli., Bd. I, 1894; Torvier, Arch. f. Entwickelutigsmech . 

 Bd. 20, 1905; Braus, op. cit. 



^Harrison, Am. Journ. Anat., vol. 5, 1906. 



