( 111 ) 



IX. — Some Observations on the Cuticle in relation to Evaporation. By John 

 Davy, M.D., F.R.S. London and Edinburgh. 



(Read 1st May 1865.) 



Though it is generally admitted that the cuticle performs an important part 

 in retarding and regulating evaporation from the surface of the body, yet I am 

 not aware of any inquiry hitherto made to determine the fact with exactness. 



On account of the importance of the subject, I have been induced to engage 

 in it. The experiments instituted for the purpose have all been of a very simple 

 kind and easily made. They were on the similar parts of dead animals, detached 

 immediately or very soon after the animals had been killed. From one speci- 

 men in each instance, the cuticle with the cutis, or the cuticle alone, was removed ; 

 whilst from the other these parts of the integuments were left entire. Each was 

 carefully weighed, and then suspended, exposed to the air, side by side. Day 

 after day, with occasional interruptions, or hour after hour, the weighing was 

 repeated, and the result in the loss sustained was noted down. The experiments 

 were made, when not otherwise mentioned, as just described, in a room in which, 

 except in the height of summer, there was commonly a fire by day, its tem- 

 perature during the day and night varying from about 50° of Fahr. to 55° and 58°. 

 The animals affording the subjects of the trials were the trout, frog, toad, hare, 

 rabbit, pig, thrush, common fowl, blue tit. Even at the risk of tediousness, I 

 shall give the results of the weighing in some detail, — exactness in such trials 

 being the first thing necessary. 



1. The Common Trout (Salmo fario). Two trouts were selected of the same 

 size. From one (No. 1) the greater part of the skin was removed, when it weighed 

 112 grs. The skin of the other (No. 2) was left on entire; it weighed 267 grs. 

 This was on the 20th October. 



October 21. No. 1 hacl lost 32-0 grs., or 28-5 per cent. 



>5 



j> 



2 



;> 



31-7 



?> 



19-0 



22. 



!) 



1 



)) 



55-3 



j» 



50-6 



5J 



J) 



2 



)) 



66-0 



51 



390 



24. 



>) 



1 



'J 



80-0 



!> 



71-4 



)) 



)> 



2 



)) 



108 



)) 



64-6 



27- 



3) 



1 



>) 



828 



)5 



74-0 



)J 



!> 



2 



)) 



120-8 



!] 



72-0 



28. 



;> 



1 



5) 



83-0 



It 



74-2 



J) 



5> 



2 



>! 



1213 



>•> 



72-6 



30. 



>5 



1 

 2 



') 



831 



121-8 





74-28 

 72-90 



VOL. XXIV. PART I. 2 H 



