576 POPULAR SCIENCE MONTHLY. 



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 note- 

 worthy. 



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 Mal- 

 pighi; 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 in- 

 stantaneously 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, Swammer- 

 dam 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 



