Vertebrata. Zoological Collection, 171 



On the Change which the Air in Eggs vndergoes during Incubation^ ^(By 



Professor Dulk of Koenigsberg. ) — This philosopher has lately made some 

 analyses of the air, in the large end of the eggy at different periods of incuba- 

 tion, and tiie following is the result of his inquiries : — 



Before in<;ubation, the air contains considerably more oxygen than atmos- 

 pheric air ; the oxygen in the former being found, at two different experi- 

 ments, 25.26, and 26.77, and that in the latter, on the day of the experiments, 

 only about 21.0.* 



On the tenth day of incubation, the air was found to contain 22.47 of 

 oxygen and 4.44 of carbonic acid : the absolute quantity of oxygen is accord- 

 ingly nearly the same, but 4.44 of it has united with carbon. 



On the twentieth day, the quantity of air in the egg was found to be 

 nearly eight times as large as before incubation ; the analysis gave, at four 

 different experiments: — 



Carbonic Acid. Oxygen. 



9.40 



9.23 17.35 



ai9 



BAS 17.90 



where, ihe absolute quantity is the same as in the former experiments^ bat 

 the quantity of carbonic acid is increased ; that of the third experiment, 

 being only 6.19 per cent, corresponds, however, in some degree, with the 

 result of the other analyses, as the chicken had apparently died a consi- 

 derable time before the experiment was made (^Schweigger-SeideVs JaJirh, 



tkr Chemie und Phgsik.) — Journ. of Roy. Inst. No. II. p, 433. 



On the Mode of Growth of Feathers ; by M« Frederic Cuvier* 

 M. Frederic Cuvier, who has been long occupied with investigations 

 concerning the organs which have been employed by zoologists to charac- 

 terize the mammalia, has conceived that an examination of the development 

 of feathers might throw some light upon the growth of hair. The number 

 and diversity of their parts, and the size of the organ which produces them, 

 give indeed more scope for observation. 



Notwithstanding the varieties of size,, consistence, and colour, all feathers 

 are composed of a quill, a shaft, and barbs, more or less provided with 

 barbules. 



The organ by which the feather is produced has the form of an elongated 

 cylinder, deeply seated in the skin of the bird by an extremity called the 

 umbilicus. Its most external envelope, or capsule, is composed of several 

 tunics, the outermost of which is of the nature of epidermis ; the internal 

 tunics are more compact, but have no appearance of organization. The 

 shaft and barbs pass out of the extremity of this capsule opposite to the 

 umbilicus. In the axis of the capsule is a medulla, also cylindrical, fibrous, 

 and of g;elatinous texture, adhering to the umbilicus, and receiving at 

 its point of adhesion numerous blood-vessels. Around this medulla, or 

 between it and the external envelope, are two parallel membranes, one 

 internal, and the other external, obliquely striated, or rather united to each 

 other by parallel septa, which pass obliquely from a superior and longitudinal 

 line towards a line, also longitudinal, but situated on the other side of the 

 cylinder. In the long and narrow spaces between these septa, the matter 

 of the barbs is deposited, and formed into barbs and barbules, nearly in the 

 same way as the enamel of the teeth is formed between the external mem- 

 brane of their gelatinous pith and the internal membrane of their capsule. 

 The superior smooth line, from which the striai pass, receives, and moulds 



* Though this result is somewhat at variance with that obtjiined by M. Bischoft^ accord- 

 ing to whom the mean quantity of oxygen before incubation, is only 23.475, the experi- 

 ments of both philosophers a^Tee, inasmuch as both shew that the air of fresh eggs contains 

 more oxygen than atmospheric air. 



