VOL. II.] PHILOSOPHICAL TRANSACTIONS. 225 



As in the doctrine of percussion several things are to be accurately dis- 

 tinguished, such as the percussive force, the motion or the velocity of the per 

 cussion, and the resistance of the body percussed ; and then an estimate to be 

 made of the proportion of those three to one another : this author pretends to 

 have both assigned that difference and demonstrated the proportion ; adding, that 

 though Galila^o saw and acknowledged that the force of percussion was in- 

 finite, or rather unlimited,* yet he there deferred discoursing any farther on 

 that matter. Our author pretends that that proposition concerning the infinite- 

 ness of the force of percussion, not having been yet demonstrated by any, he 

 has in this book resumed the whole matter concerning percussion, and clearly 

 demonstrated the true and genuine nature of it, its cause, properties and 

 effects. In doing which, he takes occasion to discourse also of gravity, mag- 

 netism, tremor of bodies, pendulums, &c. 



IV. Nicolai Stenonis-}* Musculi Descriptio Geometrica, Florentiag, 4to. 1667. 



This work exhibits an ingenious but unsatisfactory attempt to explain the struc- 

 ture and action of a muscle upon geometrical principles. Subjoined to it are two 

 narratives, one of which relates to the dissection of the head of a shark, which he 

 calls canis carcharia,:}: where he delivers many curious observations concerning 

 the skin, eyes, optic nerves, muscles of the eye, exceeding smallness of the 

 brain, as also concerning the mouth and strange teeth of this fish ; examining 

 withal whether glossopetrae be the teeth of this creature, or stones produced by 

 the earth ; in which controversy he takes their side who maintain that those 

 and divers other substances found in the earth are parts of the bodies of ani- 

 mals ; and endeavours to prove that such sorts of earth may be the sediments 

 of water, and such bodies the parts of animals carried down together with those 

 sediments, and in progress of time reduced to a stony hardness.^ — The other 

 narrative relates to a female dog-fish, also dissected by himself, where there 



•* That is, in respect of mere dead weight or pressure. 



f This celebrated Danish anatomist studied under his countrj'man Bartholine, and held for some 

 time the professorship of anatomy at Copenhagen. He afterwards travelled into Holland, Germany, 

 and Italy J in the last- mentioned country he resided a considerable time, during which he changed his 

 religion, becoming a catholic, and receiving some ecclesiastical appointments from Pope Innocent XI. 

 He died in l6s6, before he had attained his 50th year, Steno wrote several Latin tracts on anato- 

 mical subjects, and discovered the external salivary duct, which has since gone by his name. See 

 his Obs. Anatom. quibus varia oris, oculorum et narium vasa describuntur, novique salivae, lachiy- 

 marum et muci fontes deteguntur. Leidae, l66"2. 



X Squalus Carcharias, Linn. 



§ These glossopetrae are petrifactions of the teeth of some animal, probably some marine animal j 

 but they do not always resemble the teeth of the shark. They were once supposed to be the 

 petrified tongues of serpents^ whence their compoiuid name. 



VOL. I. F P 



