MODERNBIOLOGY 305 



perimentally. In the last-mentioned respect are observed both the contraction 

 of individual muscles when the nerves that are connected with them are 

 irritated, and the different forms of movement in man and animals — a sub- 

 ject in which Borelli and Perrault are cited as precursors. Similarly, under 

 the heading "sensibility" the nervous system is dealt with, followed by 

 the other functions of the body. The most remarkable point of this exposi- 

 tion is the detailed comparison made between the same organs in different 

 animals — a study in which Vicq d'Azyr certainly finds support in the pre- 

 liminary works of Daubenton; but the former without the least doubt carries 

 through the comparative program far more thoroughly than the latter. 



Its valuable contributions to science 

 In points of detail Vicq d'Azyr's investigations contain many contributions 

 of immense value, and also a wealth of ideas of great significance for the 

 future. He paid special attention to the comparative anatomy of the mam- 

 mals. He continued and widened the comparison of the bodily structure of 

 man and the apes which Camper had initiated, arriving, too, at the same 

 results as the latter (see Part II, p. x6o); on this subject he made a special 

 study of the musculature of the extremities, and in general closely compared 

 the extremities throughout the mammalian class. Further, he made investi- 

 gations into the teeth of the entire vertebrate class; he points out the differ- 

 ence between teeth fixed in dental sacs and provided with vascular and 

 nervous systems, and those that are fixed on the jaw-bone; he observes the 

 dissimilarity in the number and structure of teeth in mammals of different 

 structure and habits; he draws attention to the pointed teeth of the beast of 

 prey, the knobby teeth of omnivorous animals, and the enamel-coated teeth 

 of herbivorous animals; he notes the presence and absence of various kinds 

 of teeth in different animals. He points out the correlation existing between 

 different organs in animals; a certain shape of tooth presupposes a certain 

 type of structure in the extremities and the digestive canal, because all its 

 bodily parts are adapted to the animal's way of living. He also shows how 

 these different characteristics give every animal a special role to play in the 

 great struggle that is constantly going on in nature between the various 

 life -forms. The weakest point of his comparative investigations is the com- 

 parison between vertebrates and invertebrates; although he is far more cau- 

 tious than Geoffroy Saint-Hilaire was later, he nevertheless has no true eye 

 for the difference between the organs in the important main groups in the 

 animal kingdom, and, on the whole, it was certainly fortunate for him that 

 he did not find time to extend his studies to the invertebrate animals. He 

 even includes the vegetable world in his comparative studies, sometimes 

 without much success, as when he compares the symmetry in pinnate plants 

 with that of animals, and sometimes with an insight that looks far ahead 

 into the future, as when he crosses white and red tulips and finds that the 



