Book of the Week: Frogs in Trousers?

View Full Size ImagePer our user feature earlier this week on Dr. Charlotte Sleigh of the University of Kent, we feature a book that has been particularly important for Dr. Sleigh’s recent work: Dissertations relative to the natural history of animals and vegetables , volume 2 (1789), by Lazzaro Spallanzani. Dr. Sleigh’s current activities involve writing a book on the cultural history of frogs for Reaktion Books’ Animal series. In Dr. Sleigh’s own words regarding the importance of this title for her current endeavors:

“I had come across a reference to this book in relation to a strange experiment in which Spallanzani dressed his frogs in waxed taffeta trousers, to understand how fertilization took place. As hoped, I found the account of this curious experiment, alongside many more scientifically and culturally rich accounts of his work on frogs: a jumping-off point (if you’ll pardon the pun) for further research.”

Indeed, Lazzaro Spallanzani (1729-1799), an Italian Catholic priest, biologist and physiologist, made important contributions to the world of science with his work on animal reproduction, proving that it required both semen and an ovum in order to prosper. This discovery is in part due to his experiments with frogs and trousers. With such a curious experiment leading to such an important discovery, there was no doubt that this book should be featured, in all its glory, as our book of the week, and that the passage regarding frogs and trousers should be particularly highlighted.

Spallanzani had been experimenting on animal reproduction for some time before the incident with the trousers. His experiments were confined to a particular species of frog, which he identified as the “Green Aquatic Frog.” During his course of study, involving experimenting with various environmental and conditional effects on frogs for the success of fertilization, he received a letter from abbe Nollet regarding his work. In it, Nollet wrote,

“About thirty years ago, Mr. Reaumur and myself made many researches relative to this subject…I remember putting breeches of waxed taffeta on the male [frog], and watching a long time, without perceiving any appearance that denoted an act of secundation.”

Spallanzani was intrigued by the account given him by Nollet, and decided to reproduce the experiment. By his account,

“The idea of the breeches, however whimsical and ridiculous it may appear, did not displease me, and I resolved to put it in practice. The males, notwithstanding this incumbrance, seek the females with equal eagerness, and perform, as well as they can, the act of generation; but the event is such as may be expected: the eggs are never prolific, for want of having been bedewed with semen, which sometimes may be seen in the breeches in the form of drops. That these drops are real seed, appeared clearly from the artificial secundation that was obtained by means of them.”

By such means were the facts of reproduction secured, and we have the delightful image of frogs in trousers to thank for it.

Take some time to explore Spallanzani’s work on reproduction in this volume, and consider reading up on his important work on digestion, which is recounted in the first volume of this title. And let us praise the ingenuity of our forefathers, without which we might never have the opportunity to feature such delightful accounts of experiments in our books of the week!

Avatar for Grace Costantino
Written by

Grace Costantino served as the Outreach and Communication Manager for the Biodiversity Heritage Library from 2014 to 2021. In this capacity, she developed and managed BHL's communication strategy, oversaw social media initiatives, and engaged with the public to excite audiences about the wealth of biodiversity heritage available in BHL. Prior to her role as Outreach and Communication Manager, Grace served as the Digital Collections Librarian for Smithsonian Libraries and as the Program Manager for BHL.