HISTORICAL INTRODUCTION xxix 



discovered that segmenting eggs occurred in the oviducts before 

 pairing had taken place, nor did he succeed in throwing any light 

 on the problem of fertilization in the Salamander. In his posthumous 

 treatise on the terrestrial Salamander, which may be considered next 

 since the work was done before 1 839,^ he does not seem to have been 

 aware that the Amphibian heart has two auricles. He definitely says 

 it has not in Spelerpes, and as regards Salamandra he always uses the 

 term atrium in the singular. He gives a very full account, accom- 

 panied by excellent figures, of the development of the external 

 characters, from the segmentation of the egg up to the adult stage. 

 His outline of the development of the internal organs, such as the 

 gut, nervous system, and skeleton, is a very definite advance on the 

 standard of such work at his time. The anatomy of metamorphosis 

 is accurate and more detailed than any previous description, and he 

 is especially admirable on the metamorphosing skull, and on the 

 changes undergone by the muscular and vascular systems. He de- 

 scribes and figures the carotid gland,^ which he says *is actually a 

 consequence of the shortening of the artery at the moment of meta- 

 morphosis'. He did not succeed in finding the lymph hearts, but 

 describes, and beautifully illustrates, the lymphatics of the gut and 

 bladder. Perhaps, however, his most interesting discovery is that of 

 the pronephros and segmental duct, which he describes and figures 

 under the name of 'Wolffian body'. Leydig also figures these struc- 

 tures in the Salamander larva in 1857. In 1841 Rusconi becomes 

 involved in a controversy as to whether the blood-vessels of the Sala- 

 mander are morphologically inside or outside the lymphatics. For 

 some years he adhered to the former view, and insisted that the 

 blood-vessels were in direct contact with the lymph right up to their 

 smallest branches in the skin. Panizza, on the other hand, main- 

 tained that the arteries were only invaginated into the lymphatics, 

 and were related to them as the heart was to the pericardium. The 

 controversy was prolonged for some years, Rusconi repeatedly claim- 

 ing that his double and triple injection methods were superior to the 

 mercury injections of Panizza. In fact he was so convinced of the 

 soundness of his attitude that he began to get interested in questions 

 of priority, and to argue who was the first to discover this mare's nest. 



' This monograph was actually completed in 1839, when it was partly set up in 

 type. Rusconi, however, postponed publication in order to revise it, but he did not 

 live to complete this task. 



2 The carotid gland of Amphibia was discovered in the Frog by Swammerdam in 

 the seventeenth century (published 1738). He, however, describes and figures two 

 on each side, the second apparently being the thyroid gland. 



