76 
in which the presumed daughter of a particular Golden 
Eagle, remarkable for having produced eggs of very great 
beauty, has in two successive years laid eggs which un- 
mistakably resembled those of her reputed mother in the 
brilliant character of their colouring. 
Hence I am not afraid of hazarding the supposition, that 
the habit of laying a particular style of egg is likely to 
become hereditary in the Cuckow’;; just as I have previously 
maintained that the habit of depositing that egg in the 
nest of a particular kind of bird is also likely to become 
hereditary. 
Now it will be seen that it requires but only an applica- 
tion to this case of the principle of “ Natural Selection” or 
“ Survival of the Fittest” to show that if my argument be 
sound, nothing can be more likely than that, in the course 
of time, that principle would operate so as to produce the 
facts asserted by the anonymous Solognot of a hundred 
years ago, and by Dr. Baldamus and others since. The 
particular gevs of Cuckow which inherited and transmitted 
the habit of laying in the nest of any particular species of 
bird eggs having more or less resemblance to the eggs of that 
species, would prosper most in those members of the gems 
where the likeness was strongest, and the other members 
would (ce@teris paribus) in time be eliminated. It is not to be 
supposed that all species, or even all individuals ofa species, 
are duped with equalease. The operation of this kind of 
“Natural Selection” would be most marked in those cases 
where the species are not easily duped, that is, in those 
cases which occur the least frequently. Here it is that we 
find it, for it has been shown that eggs of the Cuckow, de- 
posited in the nests of the Red-backed Shrike, of the 
Bunting-Lark, and of that bird which for some reason best 
known to the donor bears the English name of “ Melodious 
Willow-warbler,” approximate in their colouring to the eggs 
of those species—species in whose nests the Cuckow rarely 
(in comparison with others) deposits hereggs. Of species 
which would appear to be more easily duped, or duped in 
some other manner—the species in whose nests Cuckow’s 
eggs are more commonly found, I may have something to 
say in another paper. ALFRED NEWTON 
THE ORIGIN OF BLOOD-LETTING 
HE flamingo in the gardens of the Zoological 
Society has recently been observed to vomit a red- 
coloured fluid over certain smaller birds kept with it; 
and it has been shown that this red fluid contains true 
blood-corpuscles, and inferred that the flamingo is in the 
habit of feeding its young by this ejection of a blood- 
stained “ pigeon’s milk” into their mouths. Further, the 
habit of the flamingo has been with great probability 
connected with the story of the pelican, which, as is well 
known, is stated to wound its own breast in order to feed 
its young with the blood. It is not at all improbable 
that birds so alike in their plumage and habitat as the 
pelican and flamingo should be confused in the way sug- 
gested by Mr. Bartlett, who, I believe, first observed 
the habit of the captive flamingo. The extravasation of 
blood corpuscles normally from the pharynx or cesophagus 
of such an animal is a matter of great interest. Mr. 
Lowne has a paper in the Journal of the Queckett Micro- 
scopical Club, in which he gives a full account of the case, 
having examined the bloody exudation microscopically. 
NATURE 
| Nov. 18, 1869 
To this the reader is referred; but I have something to 
add to it. 
The connection of the flamingo with the classical story 
of the pelican’s self sacrifice is increased in interest, 
since it appears that the red exudation of the hippo- 
potamus is connected with an equally ancient and more 
important tradition—namely, the history of the origin 
of blood-letting. Before giving this tradition, I would 
mention that two years since, by the kindness of Dr. 
Murie, I obtained some of the red exudation of the hippo- 
potamus on a slip of glass, and on examining it with the 
spectroscope, I did zo¢ obtain a blood-spectrum. Mr. 
Tomes (Proc. Zool. Society, 1857) described the micro- 
scopic appearances of the exudation of the hippopotamus, 
and stated that he found in it remarkable corpuscles with 
pigmentary granules, but not 0/o0d corpuscles. The folds 
of the skin in various parts of the body of the hippo- 
potamus are coloured bright pink bya distinct pigment, and 
the same tint suffuses the darker parts of the skin. I 
believe it is this pigmentary matter which causes the red 
colour of the exudation of the hippopotamus, and that it 
is not a sweat of blood at all. The case of Mr. Jamrack’s 
rhinoceros mentioned by Mr. Lowne may be otherwise. 
Mr. Lowne says that cases of blood-stained sweat from 
the skin of man are, though rare, well authenticated. 
This is perhaps true ; but many apparent cases of such 
staining are due to the formation of a purpurate in the 
sweat, from the decomposition of the uric acid which it 
contains. 
Now, with regard to the hippopotamus, it is important 
to note how popular tradition has attributed the origin 
of a very valuable medical art to a totally false inference 
on the part of Egyptian priests. 
M. Milne-Edwards, in the 3rd volume of his “ Lecons sur 
la* Physiologie” (p. 3), has the following note :—“‘ Homer, 
whose poems constitute a sort of encyclopaedia of the 
science which the Greeks possessed about the ninth cen- 
tury before Jesus Christ, does not speak of bleeding: but 
if we are to believe an author of the fifth century, Stephanus 
of Byzantium, this operation was known to the surgeons 
of the army of Agamemnon. In fact, he relates that one 
of them, Podalirius, son of A<sculapius, and brother of 
Machaon, on the return from the siege of Troy, practised 
it on a patient whose cure obtained for him the sovereignty 
of the Chersonese. This would be the first case of 
blood-letting of which the remembrance has _ been 
preserved ; and, on consideration of a fable reported by 
Pliny, I am induced to believe that this practice had 
taken its rise in Upper Egypt: in fact, this naturalist 
tells us that the hippopotami, when they become too obese, 
have the habit of piercing for themselves the vein of the 
thigh, by pressing against a pointed_reed ; and that these 
animals have thus taught physicians to practise analogous 
operations. Now, this account does not apply to the sea- 
horse (or Syzgvathus), astheauthor of an estimable work on 
the history of medicine (Leclerc) supposes, but to the great 
pachyderm which inhabits the rivers of the interior of 
Africa, and which is foundin Upper Egypt. Itis evidently 
a fable : but this fable could only have reached us from 
Egypt.” 
M. Milne-Edwards was not aware of, at any rate does 
not refer to, the red oozing observed on the skin of the 
hippopotamus sometimes after emerging from his bath, 
