BY D. EMBLETON, M.D. 79 



the descending egg in a spiral course. Whether the oviduct of 

 the birds previously cited have the same sort of spiral ''rifling" 

 I do not know, and it would now be perhaps ''illegal" to at- 

 tempt to ascertain. 



It is a curious and instructive fact that the foetus of the hu- 

 man being, and perhaps also of other Mammalia, likewise per- 

 forms, during parturition, a similar spiral movement of about a 

 quarter of a circle, and that, as a rule, from left to right, but 

 occasionally also from right to left. 



The logical conclusions then seem to be, that there is a consi- 

 derable similarity between the parturition of the avian and that 

 of the human ovum, in many of the particulars .which make up 

 that complicated and wonderful process ; that there is also every 

 probability that the ground colours of eggs are owing to albumen 

 and mucus secreted by a mucous membrane in a state more or 

 less decided of congestion or quasi-inflammation ; and fui^ther, 

 that the markings of various kinds are the result of small escapes 

 of blood from the overcharged vessels of the membrane which 

 have been abraded or ruptured by the rough calcareous coating 

 of the egg as it is rubbed against them by the forcible contrac- 

 tions of the muscular wall of the oviduct. 



yi. — Although the above conclusions may be admitted as pro- 

 bable, it may be very pertinently urged that no actual or distinct 

 proof has been adduced in support of them, and that it is neces- 

 sary to ascertain what light further research may throw on the 

 subject. 



To meet such reasonable objection the spots on eggs, chiefly 

 of the Peewit, have been subjected, by one of my friends, to ex- 

 amination by the microscope, as well as to spectroscopic and 

 chemicah analysis, and with the following results. 



The microscope has hitherto given no clue to the nature of the 

 spots on the eggs of birds, either when they were examined alone, 

 while dry or wet, or after having been treated in various ways 

 with diiferent re-agents : no blood disks were discovered. It must 

 however be added, that very commonly when blood is congealed 

 on a glass slide, and submitted to a microscope of sufficient power, 



