Page:Popular Science Monthly Volume 58.djvu/584

576 Fig. 5 shows reduced sketches of his illustrations of the structure of the snail, and also of the larva of an insect. The upper sketch on the left-hand side shows the central nervous system and the nerve trunks connected therewith, and the lower figure on the same side shows the shell and the principal muscles. This is an exceptionally good piece of anatomical work for the time, and is a fair sample of the fidelity with which he worked out details in the structure of small animals. Besides showing this, these figures also serve the purpose of pointing out that Swammerdam's fine anatomical work was by no means confined to insects. His work on the structure of the young frog was equally noteworthy.

But we should have at least one illustration of his handling of insect anatomy to com j are more directly with that of Malpighi, already given (p. 567)-The right-hand side of Fig. 5 is a reduced sketch of the anatomy of the larva of an ephemeras, compared with the work of Malpighi; we see there a more masterly hand at the work, and a more critical spirit back of the hand. The nervous system is very well done, and the greater detail in other features shows a disposition to go into the work deeper than Malpighi.

Besides work on structure and life histories, Swammerdam showed, experimentally, the irritability of nerves and the response of muscles after their removal from the body. He not only illustrates this quite fully, but seems to have had a pretty good appreciation of the nature of the problem of the physiologist. He says:

"It is evident from the foregoing observations that a great number of things concur in the contraction of the muscles, and that one should be thoroughly acquainted with that wonderful machine, our body, and the elements with which we are surrounded, to describe exactly one single muscle and explain its action. On this occasion it would be necessary for us to consider the atmosphere, the nature of our food, the blood, the brain marrow and nerves, that most subtle matter which instantaneously flows to the fibers, and many other things, before we could expect to attain a sight of the perfect and certain truth."

In reference to the formation of animals within the egg, Swammerdam was, as Malpighi, a believer in the preformation theory. The basis for his position on this question has already been stated.

There was another question in his time upon which philosophers and scientific men were divided, that w T as in reference to the origin of living organisms: Does lifeless matter, sometimes, when submitted to heat and moisture, spring into life? Did the rats of Egypt come, as the ancients believed, from the mud of the Nile, and do frogs and toads have a similar origin? Do insects spring from the dew on plants? etc., etc. The famous Redi had performed his noteworthy experiments the year after Swammerdam's birth, but opinion was divided upon the question as to the possible spontaneous origin of life, especially among