SEVENTEENTH AND EIGHTEENTH CENTURIES 155 



merits of the body. On all these subjects he expresses original opinions, 

 constantly pointing out comparisons with mechanical organizations in ani- 

 mate nature, and in doing so he displays throughout his capacity as a prac- 

 tical technician. Thus, he compares the muscles which act counter to one 

 another in an arm with the shrouds on a boat-mast which counterbalance 

 one another; in another connexion the valves of the heart are compared with 

 the mechanism of a sluice-gate. His study of the mechanism of the auditory 

 organ is full of striking observations; in regard to the visual organ, too, 

 he makes some interesting comparisons — for instance, between the lenses 

 in different animals — although naturally the results of modern optics, 

 founded by Huygens and Newton, are unknown to him. In every case he 

 tries in the first place to ascertain the nature of the movements performed 

 by the different parts of the body; consequently he pays special attention to 

 the structure and function of the muscles; in contrast to Borelli, however, 

 he entertains the false idea that it is not "the flesh," but the interposed 

 lengthwise and crosswise fibres — that is to say, the connective tissue — 

 which expands and contracts. He gives a detailed description of this proc- 

 ess; he believes that the muscle in its natural position is contracted; when 

 it relaxes, it does so because the nerves convey to the muscular fibres a 

 "substance sfiritueuse,'" which expands them just as metals are expanded by 

 heat. The motory impulses therefor come from the brain; of its parts he con- 

 siders the medulla oblongata to be the most essential and the great brain the 

 least important; he had, indeed, observed that it is possible to remove the 

 great brain from a live dog without the animal's dying, but if the medulla 

 oblongata is injured the dog dies at once. This fact the physiology of our own 

 day has, of course, confirmed, although the conclusion which Perrault draws 

 from it as to the lesser importance of the great brain is wrong. To "peris- 

 taltics," by which he means the movements within the body, he devotes 

 a special chapter, which likewise contains many keen-sighted observations, 

 the process of nutrition as a w^hole being of particular interest to him; natu- 

 rally, however, he has a number of false ideas as to its chemistry, such as 

 his belief that the air contains directly alimentary constituents, proved by 

 the fact that some broods of serpents, which were kept in a jar without 

 food, developed "on air." Owing to the limited possibilities of investi- 

 gation in those days, we cannot blame him for being unable to discover that 

 animals have an embryonic reserve nutriment to live on. 



In spite of occasional fallacies, Perrault may thus be regarded, side by 

 side with Borelli, as one of the pioneers of modern biology. Besides these, 

 the Danish philosopher Steno, well known for the strange fate that befell 

 him, is worthy of mention as having been active in the same direction. 



Nils Steensen, known under the latinized form of his name, Nicolaus 

 Steno, was born in Copenhagen in 1638, of a wealthy family of goldsmiths. 



