2 4 o SCIENCE PROGRESS 



experiments on bats were carried out. The house has been 

 identified, and in the attic some interesting relics were dis- 

 covered in the strings and dried-up pipistrelles used by him in 

 these investigations. He blinded the animals sometimes by 

 burning the eyes with a red-hot wire and sometimes by removing 

 the organs altogether, and even filling up the orbital cavity 

 with wax. Notwithstanding these mutilations, the little 

 creatures were able to fly as well as before, avoiding the walls, 

 and the strings suspended in the path of their flight. These 

 and other experiments led him to the conclusion that bats find 

 their way in the dark by means of some special sense situated 

 in an unknown organ in the head. It is now generally accepted 

 that this astonishing faculty in bats of directing their flight is 

 due to an exceptional development of the sense of touch, espe- 

 cially in the wing membranes. 



Before finding fault with the brutality of Spallanzani as 

 an experimenter, it is just to remember that his passionate 

 curiosity led him to turn his ruthless hand even against himself. 

 For in his Studies in Digestion x he describes how he swallowed 

 bone, cartilage, and tendon concealed in perforated wooden 

 tubes, and how, in order to obtain gastric juice for the purposes 

 of artificial digestion, he caused himself to vomit on an empty 

 stomach by tickling the fauces. This knowledge ought to soften 

 the heart of the most fanatical zoophilist towards the Abbe. 



In August 1779 we find him in Switzerland on a visit to 

 his friend Bonnet at the latter 's " delightful villa " at Genthod. 

 Abraham Trembley was also present, and one likes to think of 

 these three with heads bent and hands folded behind the 

 back walking and talking together, each of them engaged upon 

 researches of great moment in biology — Bonnet perhaps on his 

 studies of asexual propagation in Aphides, Trembley on regen- 

 eration in Hydra the fresh- water Polyp, and Spallanzani occupied 

 just then with fertilisation in toads. In Bonnet's presence he 

 cut off the hind legs of a male toad during its embrace of the 

 female without effecting a separation. The female, he points 

 out, may begin to discharge eggs later, and the male with 

 his blood flowing all the time continues to impregnate them 

 with his semen. In reply to a question, " he did not hesitate 

 to say that this persistence was less the effect of obtuseness of 



1 Proving the theory of digestion by solution as against the principle of 

 trituration. 



