Aprit 8. 1897] 
NATURE 53 
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clature, and chemical calculations. At the end of each 
chapter is a summary, and a number of questions to test 
the student’s progress. Considerable attention is given 
to experiment, and the aims and purposes of the study of 
chemical science are brought into prominence. -In fact, 
though the volume is one of a class of much-maligned 
text-books, and though it is intended for students working 
for examination, it is, nevertheless, a book which presents 
the rudiments of chemistry in a form which will make 
students appreciate the value of experiment as an instru- 
ment of scientific research. 
Encyclopédie scientifique des Aide-Mémoire. Edited by 
M. Léauté. (Paris: Gauthier Villars et Fils. Masson 
et Cie.) 
THREE new volumes have recently appeared in this very 
serviceable series of technical handbooks. ‘They are as 
follows :— 4 
“Tes Piles Electriques.” By Ch. Fabry. This volume 
deals with the theory of the various electric cells, the 
measurement of the electromotive force and resistance 
of such cells, the construction of ordinary electric cells, 
and standard cells. 
“Les Machines Thermiques.” By Prof. Aimé Witz. 
Heat engines generally, steam engines, hot-air engines, 
and gas engines form the main subject of this volume. 
The object of the book is to institute a comparison 
between various heat machines, so as to bring into 
prominence the special characters of their respective 
cycles. Chapters are devoted to atmospheric machines, 
compressed-air machines, and freezing machines. Ele- 
mentary students of thermo-dynamics will find the book 
interesting. 
““Les Gaz de l’Atmosphére,” by M. H. Henriet, is an 
excellent little volume on the chemistry of the atmo- 
sphere. The author is chemist at the Montsouris Ob- 
servatory, and the methods of analysis described by him, 
as well as the results of investigations into the com- 
position of the air at different places and at different 
times, makes his little book very valuable to meteoro- 
logists as well as chemists. 
The Dahlia: its History and Cultivation. By various 
Writers. Pp. 81. (London: Macmillan and Co., 1897.) 
THE history of the dahlia is told in this handbook by 
Mr. Richard Dean ; the botany is described by Mr. John 
Ballantyne ; the propagation and exhibition of the dahlia 
are dealt with by Mr. Stephen Jones ; and the cultivation 
by ‘Mr. Robert Fife; while Mr. William Cuthbertson, 
the editor of “Dobbie’s Horticultural Handbooks,” to 
which series the present volume belongs, contributes an 
introduction. The book is interesting to the botanist as 
well as the florist, and it should be possessed by every 
one who finds delight in cultivating dahlias. Of especial 
value to floriculturists is a full and classified catalogue of 
varieties of the dahlia, and selections for various purposes. 
The varieties are arranged alphabetically, and the charac- 
teristics of each are described. 
La Cause Premitre d’apres les Données Expérimentates , 
By Emile Ferriére. Pp. 462. (Paris : Félix Alcan, 1897.) 
THIS volume is the third and last of a trilogy having 
for their object the demonstration of the unity of sub- 
stance by means of established facts, @ fvoré argument 
being excluded. In the first volume the unity of the 
laws of matter and energy throughout the universe was 
expounded ; the second volume dealt with the physical, 
physiological, embryological, and pathological facts con- 
cerning hfe and mind ; the present volume aims at ex- 
plaining the relations between various forms of organic 
life, the order of appearance of animals and plants upon 
the earth, and evolution problems generally. Leaving 
the metaphysical side of the book out of consideration, 
the book contains a certain amount of readable in- 
formation and criticism. 
NO. 1432, VOL. 55 | 
LETTERS TO THE EDITOR. 
(The Editor does not hold himself responsible for opinions ex- 
pressed by hes correspondents. Netther can he undertake 
to return, or to correspond with the writers of, rejected 
manuscrapts tntended for this or any other part of NATURE. 
No notice zs taken of anonymous communications. | 
Acquired Immunity from Insect Stings. 
May I beg to add a few lines to the very interesting corre- 
spondence and discussion regarding the immunity of man from 
insect-stings and snake-bites after successive inoculations. The 
letter of Dr. Dawson Williams, in NATURE of March 4, calls 
attention to a certain degree of immunity which obtains among 
the Norwegians from the stings of the myg, a kind of gnat 
(probably our midge, Anglo-Saxon mygge). His statements in 
regard to the degree of immunity varying in different 
individuals, is quite in accordance with our experience with the 
mosquito. His pathological description of the effects of the 
sting of the Norwegian myg would apply most accurately to the 
sting of the mosquito. We also become more or less immuned 
from the mosquito poison after much suffering in childhood. 
The swelling resulting from the mosquito sting will often close 
the eyes of an infant. In middle age the sting is hardly 
noticeable. English and Irish people, upon first coming to this 
country, suffer beyond measure, and often come under the care 
of a surgeon. It is a curious yet painful sight to see a brawny 
Englishman presenting the appearance of our young infants 
under the infliction of these pests. I have two Irish servants, 
who have been in this country two and seven years respectively. 
They both tell me that the mosquito bite, as it is called, no 
longer troubles them, though they were eloquent in the de- 
scriptions of their acute sufferings at the outset. More than a 
quarter of a century ago Dr. J. C. White, a distinguished 
dermatologist, of Boston, in a communication to the Boston 
Medical and Surgical Journal, November 9, 1871, discusses the 
subject fully in a paper entitled, ‘‘On the protection acquired 
by the human skin and other tissues against the action of 
certain poisons after repeated inoculation.” He not only shows 
the immunity arising from the repeated stings of mosquitos, but 
notices a like immunity arising from the, domestic pests, 
Pediculus, Cimex and Pulex. An American recalls his first 
experiences with the flea in Europe with the same horror that 
an Englishman remembers the welcome he received from the 
mosquito in America. 
More than a century ago attention was called to the immunity 
enjoyed by natives to the sting of mosquitos. In the efforts of 
Great Britain to suppress the revolt in the American colonies, 
European troops were hired to augment their armies. Among 
these were the Anspach-Bayreuth troops, and this contingent 
was accompanied by an intelligent surgeon, Dr. Johann David 
Schoepll. His letters to Prof. Delius, of Erlangen, on the 
“© Climate and Diseases of America,” were published in pamph- 
let form in 1781. Dr. James R. Chadwick, of Boston, translated 
the pamphlet as being one of medico-historical interest. The 
following paragraph from these letters is of interest. The 
author says: ** One fact is worthy of mention in this connection, 
which perhaps testifies as forcibly as anything can to the 
need of acclimatisation, and is moreover universally admitted 
to be true. Ina new-comer, almost every bite of the mosquito 
produces a boil during the first year after his arrival, but fails 
to have this effect in the subsequent years.” 
Epwarp S. MorsE. 
Salem, Massachusetts, March 22. 
To the query of Mr. Dawson Williams (NATURE, March 4, 
p- 415), as to whether the mosquito injects a toxin, an affirmative 
answer may be given. The mosquito has, instead of the two 
long simple salivary glands of other diptera, a complex system, 
three glands on each side of its thorax, two of each set unlike 
the third. All the six ductules from these glands unite so as to 
carry the secretion to the common salivary duct, and by it to the 
hypopharyx. The structure of the hypopharyx is the same as 
that of the sting of a bee, a tubular-pointed organ with a 
subterminal orifice. The only exit for the discharge of the 
complex glandular apparatus is into the wound made by the 
lancet-formed mouth-organs. 
I have all this mechanism dissected out and preserved for 
