294 THE LIFE OF A BIRD. 



Some experiments have, however, been per- 

 formed by Mr. Towne, which leave the whole 

 matter in the greatest perplexity, and appear to 

 upset all previous notions on the respiration of the 

 chick in the shell. Mr. Towne's doubts 3n the sub- 

 ject of respiration through the medium of the blood- 

 vessels and membrane before mentioned, which are 

 for that purpose near the outer lining of the shell, 

 were excited by finding that during incubation 

 the lining membrane of the shell becomes very 

 much thickened, until it assumes the appearance 

 of parchment, thus presenting a considerable 

 obstacle to the passage of air through it, instead 

 of, as might have been expected, becoming thinner, 

 or at any rate remaining unaltered, so as to afford 

 no unnecessary obstruction to the passage of air 

 through its pores. It appeared therefore unlikely 

 that respiration could be carried on with the 

 necessary freedom through this thickened mem- 

 brane. It is deserving of remark, that in the 

 experiments of varnishing the egg, performed by 

 other observers, an innocuous varnish had not 

 been employed, and consequently it was scarcely 

 just to consider, in the experiments mentioned, 

 that the death of the chick was solely attributable 



