0"T' LAERT> "! - USP

2,66 RECENT TIMES.
the sense of taste. MALPIGHI located the sense of touch
in the papillae of the skin. BOHN referred to the distinction
between the senses of touch and of temperature, and the
Genevese philosopher, BONNET, already raised the question
whether the tongue possesses different nerves for every
kind of flavour, and the ear different fibres for every
note*
Amongst the most weighty questions engaging the atten- '%
tion of the natural philosophers of the 17th and 18th
centuries may be reckoned the theory of the generation and
development of the animal embryo. Here, too, it was
WILLIAMHARVEY who gave to these investigations a firm $
basis in enunciating the proposition, Omne animal ex ovo.
He taught that the embryo developed from the ovum which
took its origin from the mother, the semen of the male only
setting the process in motion. The opinion was maintained
that during coition the ovum is released from the ovary;
but KERCHRING remarks that women had told him that an*
ovum may be expelled at each menstruation.f The ovum
theory was put on a still firmer foundation by SwAMMER- i
DAM, MALPIGHI, and REDI, who gave a wider significance
to the HARVEIAN dictum by changing it into Omne vivum
ex ovo, and even applied it to plants. This doctrine sus- |
tained a great shock in consequence of the discovery of-'the i
spermatozoa, which J. HAM was the first to notice in 1677.
LEEUWENHOEK confirmed this observation, and described |
the spermatozoa as extraordinarily small creatures, each •
provided with a tail and a rounded head, and engaged in
continual movement; and in view of these facts he put ,1
forward the hypothesis that the spermatozoa and not the ova
form the real germs of the embryo. HARTSOEKER thought |
he recognized a resemblance between the spermatozoon and i
the human form, and looked upon each as a primitive "J
embryo. The witty LEIBNITZ even spoke of the immortality
of spermatozoa. ANTONIO VALLISNERI put an end J
* Letter of BONNET to HALLER, in HAESER. op. cit. ii, 596.
t TH. KERCKRING: Anthropogenia ichnographica, Amstelod. 1671, p. 3.