O. N. Rood on Stereoscopic Experiments. 199 



rated from other mammals, and justly forms a sub-class bj 

 himself, even without regard to his mental phenomena — if it 

 were posssible to conceive of their absence in such a structure. 



The significance of the other sub-classes also is more evident, 

 when we consider their size and organic development rather 

 than their mere brain structure. Hence Prof Dana has sug- 

 gested to the writer the terms Macrencephala and Micrence- 

 phala for Gyrencephala and Lissencephala, the one being prin- 

 cipally of large forms and the other— with the exception of the 

 Edentata which however show a sluggish overgrowth— of cor- 

 responding small forms. 



The Lyencephala would seem also to be better characterized 

 by the short gestation and the premature birth of their young, 

 than by the greater or less development of their corpus callosum ; 

 though such indications of an unfinished structure are interest- 

 ing confirmations of their premature condition. It might also 

 be objected that the term is too much like Lissencephala to be a 

 really good ( 



It is inter 

 microcephals, thaFthe typic development may 1 

 a vegetative growth or mere increase in size rimy otm w^l.i.ui^ 

 in the part so arrested ; indicating two kinds of forces, typic or 

 formative, and nutritive. The former of these is essentially 

 hereditary, governs the embryonic life and form, and gives rise 

 niore especially to the varieties of a species; the latter produc- 

 tive of growth and health is rather influenced by the conditions 

 oHife, food, &c.— w. c. M.] 



Jfew Haven, Aug., 1863. 



-^T. XVlll.— On some Stereoscopic Experiments; by Professor 



O. N. EooD, of Troy, N. Y. 

 1. On (he Binocular Combination of Drawings in fine and thick lines. 



Several years ago, Dove studied the curious effects produced 

 by the stereoscopic union of linear drawings, in which the right 

 and left hand projections were executed in different colors. Re- 

 lated to this in a certain dec^ree is the case of the binocular 

 ^nion of drawings in the same color, but with the corresponding 

 Partsconsistingof fine and thick lines. . . » 



I made in this manner, on a white ground, two projections of 

 f convex pyramid; the lines of the right hand picture having 

 three times the diameter of the corresponding lines ot the lett. 

 f oth sets of lines were black. In the stereoscope the relief was 

 ;?iind to be but little impaired, although no proper fusion of 

 je fine and thick lines had taken place: it was found, that 

 ^e fiae Unes of the one projection combined with the edges 



