XXII LIFE AND WORKS OF NICOLAUS STENO 



mentioned the reproductive organs, set forth as his opinion, that the 

 organs of the female mammals, in his days invariable named testes, 

 were not to be regarded as organs corresponding to the testes of the 

 male mammals; that they were, in fact, the same organs as the ovaries 

 of the oviparous animals; that they produced eggs and conse* 

 quently ought to be called ovaries. This was quite a new aspect of 

 these organs. Steno does not go into details about this discovery, but 

 he adds that he hopes to be able to take up the matter for further 

 treatment at a later period. His thoughts, however, became occupied 

 with many other matters, and he never wrote the intended large 

 work. The fact of his having collected materials for it appears from 

 two small Treatises in Acta Hafniensia. The investigations, upon which 

 these Treatises are based, were, no doubt, made in close connection 

 with the work just mentioned, but they were not published till 1675, 

 in which interval — in 1672, five years after Steno's first communication 

 — de Graaf had published his famous observations, and so he, quite 

 justly, obtained the credit of the discovery of the true nature of the 

 mammalian ovaries. As Gosch points out, it is well worth mentioning 

 that de Gvaaf's view was so long in being universally accepted, be* 

 cause it was observed that those formations in the ovaries, which 

 were supposed to be eggs, did not loosen nor were carried away as 

 such, which difficulty would probably have been of less importance, 

 in case it had fallen to Steno's lot to promulgate the discovery, for al* 

 ready in his first brief communication he expressed himself as follows : 

 Non amplius dubito, qvin mulierum testes ovario analogi sint, qvocunqve 

 demum modo ex testibus in uterum sive ipsa ova, sive ovis contenta materia 

 transmittatur &c. 



The two Treatises of Steno's, which have just been mentioned, con;: 

 tain much of considerable interest. Suffice it here to call attention to 

 the series of observations on the development of the plagiostomes, 

 which is found in the second Treatise. Already Aristotle relates, how 

 in the shark Galeus Ixvis the egg is not only fully developed in the 

 uterus, so that the fish becomes viviparous, but is also fastened to the 

 uterus in a similar way as in the mammals, so that the fetus has both 

 an umbilical cord and a placenta. As far as is known, no one had made 

 this observation between Aristotle and Steno, who, however, in his 

 communication says nothing of his being acquainted with this passage 

 in Aristotle. After having given a more detailed description of other 

 anatomical features of this shark (Galeus Ixvis) Steno proceeded to 

 mention another shark (Acanthias vulgaris), also viviparous, also in pos* 

 session of a yolk*sac and vitelline duct, but without a placenta. — Sub* 

 sequent investigators found no shark with a placenta, until Johannes 

 Miiller succeeded in finding once more what Aristotle and Steno had ob* 

 served. This scientist pointed out that the reason, why others had not 



