ence of the nervous system. Stimulation of the sciatic on one side 
with a subminimal electric current causes rigor to appear later on 
that side. 
The disappearance of rigor is not due to the fact that putrefaction 
liquefies a coagulated proteid. Putrefaction and rigor do not run 
parallel courses ; frogs are occasionally found in a state of rigor in 
spite of intense putrefaction. If putrefaction be checked by in- 
jection of carbolic acid or corrosive sublimate into the blood-vessels 
of the animal the rigor disappears just as quickly as in an animal 
in which putrefaction is given full sway. 
Bierfreund regards as highly significant the fact that rigor 
V. ..^v. .x.«uv^xj ,^x v..^ x^iu^^v..^ fibre ; but by what s 
stimuli this contraction is called forth, he leaves us still 
-U. D. Jordan, Boston. 
The Mechanical Origi]^- ( 
LiA. — A paper on this 
American Philosophical I 
structures o 
broadly to the two general classes, excess of growth and defect of 
growth. Each of these may be again divided into two " ^'' 
Excess of growth j£~-„^i^^^^ 
Defect o, growth] D^-y. 
The paper dwelt principally with the first two conditions, which 
have frequently co-operated "^ in the development of structures. 
These were classified under the following mechanical energies as 
A. Motion in articulation. 
1. Impact only. 
Facetting of distal end of radius in Diplarthra. 
Expansion of proximal end of radius in Diplarthra, 
Grooving of distal end of tibia by astragalus. 
Grooving of proximal end of astragalus by tibia. 
External trochlea of humerus in Rodentia (Leporidfe), and raeta- 
podials and humerus in Diplarthra. 
2. Torsion only. 
Alternation of carpal bones in Anthropomorpha. 
Symmetrical flanges of ulnar cotylus m Anthropomorpha . 
Unsymraetrical flanges of ulnar cotylus in other n 
Rounding of head of radius in Edentata and Quad 
Involution of eygapophyses in Diplarthra, etc. 
3. Torsion and impact without flexure. 
Alternation of carpal and torsal bones in Ungulata. 
