438 Dr. J. C. Ewart. On Rigor Mortis in Fish, [June 16 y 



left orbital sinuses, and running in the floor of the skull immediately 

 caudad of the pituitary fossa. 



I find that this anastomotic trunk is present in Mustelus antarcticus r 

 in which species, however, it hardly deserves the name of sinus, 

 being only 1 mm. in diameter in a dog-fish 1 metre long. Its median 

 portion is situated, not in the actual cartilage of the skull -floor, but 

 in the thick perichondrium of the pituitary fossa, where it lies- 

 immediately dorsad and caudad of the arterial commissures w (fig. 6, 

 Plate 35) at their point of crossing. Passing laterad on either- 

 side it pierces the cartilage of the cranial floor, and finally enters the 

 orbit by an aperture placed just cephalad of the trigeminal foramen, 

 and about 5 mm. caudad of the carotid foramen. 



I doubt whether this can be the anastomotic trunk described by 

 Robin (see p. 712), since it is not situated " derriere les orbites," and. 

 can hardly be described as " un sinus plus ou moins vaste." 



The vessel in question ought to have been shown in the diagram,, 

 fig. B (p. 723) as a narrow trunk connecting the orbital sinuses {orbit, s.), 

 and should have been referred to in the general account of venous 

 anastomoses on p. 722. 



XXV. " On Rigor Mortis in Fish, and its Relation to Putrefac- 

 tion." By J. C. Ewart, M.D., Regius Professor of Natural 

 History, University of Edinburgh. Communicated by J- 

 Burdon Sanderson, F.R.S. Received June 6, 1887. 



1. The Nature of Big or Mortis. 



It has been long recognised] that rigor varies extremely not only 

 in the time of its appearance, but also in its intensity. It may be 

 well marked and resemble closely a spasm, or so indistinct that it is. 

 better compared to a stiffening than to a contraction of the muscles. 

 So much is this the case that it might be convenient to describe 

 rigor as accompanied with contraction in some cases and with 

 stiffening in others. I have often noticed that when rigor comes on 

 immediately after the loss of muscular irritability, it looks extremely 

 like contraction ; but when it is postponed for days, by lowering the 

 temperature or otherwise, it more closely resembles coagulation. I 

 am inclined to believe that whether the rigor resembles a contraction 

 or a mere stiffening depends on the condition of the nervous system. 

 If the coagulation of the myosin takes place at or about the same 

 time as the death of the nerves, the rigor will to a certain extent 

 be physiological, and simulate a contraction in the extension of 

 the fins, the bending of the trunk, &c. ; whereas if the coagulation 

 only sets in some hours, or it may be days, after the death of the 



