230 
Proceedings of the Royal Society of Edinburgh. [Sess. 
X. — The Structure of the Reproductive Organs in the Free- 
Martin, with a Theory of the Significance of the Abnormality. 
By D. Berry Hart, M.D., etc., Edinburgh.* (With Two Plates.) 
(MS. received November 15, 1909. Read November 22, 1909.) 
The apparent prodigality with which Nature provides for the reproduction 
of plants and animals has a marked exception in the case of sterile 
organisms, often produced on a large scale, in which every function except 
that of propagation may be carried on in a quite perfect manner. The 
cases of the sterilisation of an organism are best seen in insects, but I 
wish at present to consider its occurrence high up in the animal kingdom 
in the well-known case of the Free-Martin, an apparent sterile cow born 
co-twin with a potent bull. 
The nature of the free-martin is considered one of the unsolved 
problems of anomalous sex. John Hunter, who first drew attention to it, 
speaks of it as an unnatural hermaphrodite. “ Hermaphrodites may be 
divided,” he says, “ into two kinds, the natural and the unnatural. The 
natural hermaphrodite belongs to the inferior and more simple genera of 
animals, of which there is a greater number than of the more perfect : 
just as animals become more complicated, have more parts, and each part 
is confined to its particular use, a separation of the two necessary families 
for generation has taken place” (op. cit., p. 46). Sir James Simpson, in 
his well-known paper, after enumerating the paradoxes in the knowledge 
at that time of the free-martin, says in conclusion : “ The whole series 
of circumstances, when considered in conjunction with each other, seems 
to form, in relation to the origin of malformations, one of the strangest 
and most inexplicable facts to be met with in the study of anormal 
development ” (op. cit., p. 835). 
Spiegelberg looked on the free-martin as a transverse hermaphrodite, 
and Geddes and Thomson say: “No theory has yet explained the facts of 
this case ” (op. cit., p. 41). 
The explanation I wish to bring forward is based on the views 
expressed in a previous paper on “ Mendelian Action on Differentiated 
Sex.” 
I must first describe the free-martin, next consider the facts known as 
to it, and then give my view as to its anomalous sex-condition. 
* From the Laboratory of the Royal College of Physicians, Edinburgh. 
