TRANSACTIONS OF THE SECTIONS. 109 



external chorion form the placenta by the umbilical vein pouring its blood among 

 the non-vascular branches of the shaggy chorion, as in the earlier stage of the 

 blastoderm capillary area ; from this the umbilical arteries receive the arterial blood 

 to be sent by the cord to the foetus for distribution through the body. The heart 

 of the foetus still continues for some time a unilocular cavity. The ventricle gradu- 

 allv grows outside of the atrium cordis, and for some time it continues as a single 

 cavity. The atrium cordis soon becomes divided into the right and left auricles. 



The ventricle in like manner becomes divided by a septum separating the right 

 and left ventricles. The aortic bulb may assist the circulation. The circulation 

 thus begun by the venous blood being sent by the umbilical vein to the placenta, 

 when the heart consisted of a single cavity, the blood would only return by the 

 arteries of the cord to the aorta through the umbilicus, and thus the course of the 

 circulation in the foetus as usually described is, according to the author, erroneous. 



Rigor Mortis not Muscular Contraction. By Dr. E. Norms. 



The commonly received theory of rigor mortis is, that it is an energetic muscular 

 contraction. That this view is erroneous is proved by the following considera- 

 tions : — 1st. That the rigor of opposing sets of muscles does not cause the redispo- 

 sition of limbs in obedience to the superior powers of the stronger sets of opponents. 

 2nd. That if either the flexors or extensors of a limb be divided and the limb be 

 placed, before rigor has set in, in the position in which it should be drawn by the 

 cut set of muscles had the action of these been unopposed, the uncut set of muscles 

 do not alter that position. 3rd. Contraction and the presence of irritability being 

 an inseparable association, it follows that if irritability be absent for a long time 

 immediately prior to the supervention of rigor mortis, the latter cannot be regarded 

 as a contraction. 4th. The microscopical appearance of muscular tissue affected 

 with rigor mortis is entirely different from that of muscular tissue in a state of con- 

 traction. The truth of these arguments he had demonstrated by a variety of ex- 

 periments, selections from which were set forth iu detail. Photographs of many 

 of the results and specimens of others were submitted to the Section. .Rigor mortis 

 is therefore not a contraction, either energetic or otherwise, of muscular tissue. It 

 is a suspension of the property of extensibility, probably due to a solidification 

 (coagulation ?) of a fibrinous (?) material contained in the intei fibrillar juices of 

 the muscles, as asserted by Briicke and Kiihne, the resolution of which by incipient 

 decomposition restores to the muscles their mobility. 



On the Early Development of Organs in Embryonic Life. 

 By Samuel H. Parkes. 



The difficulty of demonstrating the general anatomy of animals at a very early 

 period of gestation may be greatly lessened by hardening the foetus in alcohol, and 

 then making a consecutive series of very thin sections. 



A number of such preparations were exhibited, viz., fcetal rat at twenty-first day 

 of gestation ; foetal rabbit at twenty-fourth day ; foetal calf, two months ; fcetal dog, 

 two months : human foetus, two months ; and bantam chick artificially hatched. In 

 these preparations may be seen the whole of the internal organs in situ, each section 

 showing the correct relative position of organs lying in the plane of such section. 



The advanced state of development which exists at this early period in the 

 structural peculiarities of the visceral organs is truly astonishing. In the sections of 

 a human foetus (of about two months), for instance, may be seen at one view some 

 of the distinctive characteristics of cuticle, muscle, bone, spinal cord, heart, lungs, 

 liver, kidney with suprarenal capsules, spleen, intestines, and even sexual organs. 



In another central section of a bantam chick, the peculiar lung structure of the 

 bird is displayed, and the singularly beautiful insertion of rudimentary feathers. 

 Those of the rat and dog (which are made longitudinally through the centre of the 

 entire body) display the brain and whole length of spinal cord. 



In another section of a human foetus of between two and three months' growth, 

 it was seen that the vascular system had progressed to such an extent as to receive 

 a partial carmine injection. 



In carefully examining and comparing (with different degrees of magnifying 

 power) these and similar preparations made at a very early period of foetal 



