182J .] Dr. Paris on the Tkpiology of the Egg, 357 



the animal, that the smallest irregularity overthrows the nice 

 balance of the different actions that are to mature it, and produces 

 fatal effects. So solicitous, therefore, Vv^as Nature to rescue the 

 germ from the consequences of cold, that she has ordained other 

 provisions, which seem as effective as the chala^n'., for the preser- 

 vation of a due temperature. Thus is the cicatriada on all sides 

 surrounded by fluids which are extremely feeble conductors of 

 heat ; these must necessarily retard the escape of caloric, and 

 prevent the otherwise destructive chtUs which the occasional 

 absence of the parent might induce. The eggs of other animals 

 appear to be protected by an analogous apparatus. Thus the 

 ova of frogs, and some other amphibia, are enveloped in spheres 

 of mucilage, which the experiments of Spallanzani show to be 

 essential, as he found that when this gluten was removed, the 

 Qg^ immediately perished.^' It is certainly true that those fishes 

 who retail their vitality long after their removal from the water, 

 as eel and tench, have the power of secreting a slimy fluid, 

 with which they envelope their bodies ; while,' on the contrary, 

 those who, when drawn on shore, quickly die, as, for instance, 

 mackerel, possess no such faculty, or, at least, only in a small 

 degree. Is it not, therefore, extremely probable, that this albu- 

 minous matter, by repressing evaporation, and preventing, like 

 the fluids of the egg, the escape of heat by its nonconducting 

 nature, is the principal cause of this peculiar tenacity of life ; 

 perhaps a prodigious accumulation of fat may also, under cer- 

 tain circumstances, have a share in producing this effect ; the 

 silurus glanis, which is the fattest of all fresh water fislies, for it 

 grov/s to the weight of 3001b. lives very long after being taken 

 out of the water. 



Besides fishes, there are other animals who protect themselves 

 from an excess of heat, or cold, by ejecting fluids from the sur- 

 face of their bodies. The common snail is uidebted to its profu- 

 sion of slime for its |>ower of resisting cold. The fable of the 

 salamander being indestructible by fire, owes its origin to the 

 faculty which this animal possesses of discharging from the 

 numerous pores which are scattered over the surface of its body, 

 a milky fluid, by which it defends itself for a short time against 

 the fury of the flames. There is an account in the Phil. Trans, 

 of a knight, at Rome, w^ho casta salamander in the fire, which it 

 putout twice, and lived nine months afterwards ! 



The hen bird seems instinctively conscious of the mischief 

 that would accrue from an irregular or diminished temperature. 

 She is often seen to make use of her bill to push to the outer 

 part of the nest those eggs that v»'ere nearest the middle, and to 

 bring into the middle such as lay nearest the sides. The Egyp- 



* This gluten is not of the satne consistence in all the dmph'ibia : it is, for instance, 

 more abundant and viscid in frogs and toads than it is in KzaMis ai\d neWt»i -•■'-* ^' ^ 



