DEPARTMENT OF EMBRYOLOGY. 103 



in a human embiyo 6.5 nim. long, is represented by a thin layer of cells. 

 The motor nuclei arise from the thickenings of either side of the floor 

 plate in lateral ridges known as the basal plates. The narrow, thin 

 floor plate really forms the ventral midseptum of the spinal cord of the 

 brain, and subsequently commissural fibers grow through it to form the 

 raph6. If we view the basal plate from above we find that this raph^ 

 extends forward to the nem*opore, at which point the raph^ fibers 

 are the anterior commissure within the torus trans versus. Back of 

 this we have the torus opticus, and its commissural fibers are the fibers 

 of the optic nerve. At an early period in its development the torus 

 opticus evidently widens rapidly and pushes through the rest of the 

 brain, as the optic stalks appear quite suddenly. An injury to the 

 medullary plate at this time would probably make itself felt more upon 

 the optic stalk than upon the eye, since the short period during which 

 it grows rapidly is its critical one. If we cut out the optic stalk or 

 the torus opticus, as Stockard and Lewis did in their experiments, 

 then the foveola would remain together and form cyclopia. It may 

 be added that the anatomical changes found in our small cyclopean 

 human embryos, as well as in all cyclopean monsters, can be explained 

 by the removal of the structures represented along the line of the 

 raph^ of the medullarj^ plate, reaching from the mamillary bodies to 

 the neuropore. This includes the torus transversus, which naturally 

 involves the olfactory region and the anterior commissure. Thus we 

 can explain, by a study of these specimens, the anatomical changes in 

 the human brain which are found in cases of cyclopia. 



A special studj^ of the laws of bone architecture has been made by 

 Dr. John C. Koch. In this a foundation is laid for the study and me- 

 chanical analysis of the spongy bone entering into the structure of other 

 parts of the skeleton, by the appUcation of the principle that spongy 

 bone and compact bone are homogeneous material, and differ chiefly 

 in strength approximately in proportion to other densities. The thick- 

 ness and closeness of spacing of trabeculse in bone vary directly with the 

 intensity of the stresses transmitted by them. The general conclusion 

 of the study is that the law of bone holds true mathematically and 

 mechanically in the normal human femur, and therefore for all other 

 normal human bones. 



I may mention also the paper of Dr. Schultz on bilateral ossification 

 centers above the squamous portion of the occipital bone, and that of 

 Doctors Goodpasture and Wislocki on old age in relation to cell over- 

 growth in cancer. 



A developmental study of some of the primitive muscular reactions 

 in fetal and new-born kittens has been made by Professor L. H. Weed. 

 By experimental procedures he has determined the effect of decerebra- 

 tion at different stages of development, particularly as regards rhythmic 

 movements of progression. The puipose of these studies has been to 



