Eben C. Hill 459 
specimens this superficial albugineal blood supply appears as a fine mesh 
over the larger encircling arteries and veins. A few of the veins collect- 
ing from these superficial vascular lobules empty directly into the pam- 
piniform plexus, but as a rule the course is as described. 
SUMMARY. 
1. The measurements of the embryonic testis, Wolffian body and kid- 
ney from the time that the embryo is 20 mm. in length till the sex gland 
enters the internal ring are given. 
2. A comparison of the size and weight of the human testis with that 
of the adult testis of the pig is made. The comparative sizes of the 
semniferous tubules of the adult pig testis and human testis is noted. 
3. The testis of the pig receives its first blood supply when the embryo 
is 33 mm. in length, the kidney having received its blood supply when 
the embryo has attained a length of 28 mm. 
4, Out of seventy-five specimens only one exception was found to the 
usual source of the spermatic artery, and in this case the artery instead 
of coming directly from the aorta arose as a branch from the most 
caudal Wolffian artery. 
5. Marked convolutions in the spermatic artery are first evident when 
the embryo is 48 mm. in length. 
6. A change in the position of the testis relative to the remains of the 
Wolffian body is noted between 110 and 130 mm. This change is almost 
a semi-rotation; the testis assuming a more lateral position and having 
the future epididymis between it and the aorta. 
?. The entrance of the testes into the internal rings occurs when the 
embryo has attained a size of 190-220 mm. Generally the left testis 
enters first. 
8. The differences between the superficial blood supply in the human 
embryonic testis and the testes of the adult pig and mouse are indicated, 
and the relative positions of the spermatic cords to the epididymes are 
shown. 
9. The vascularization of the testis of the adult pig is diagrammat- 
ically represented, and a theory to explain the peculiarities of the ar- 
rangement of the vessels is advanced. This hypothesis is based upon a 
suggestion from Dr. Mall that the sudden growth of the testis brings 
about a backward looping of the arteries in order to supply the rapidly 
developing semi-inferous tubules. 
10. The vascularization of the tunica albuginea is illustrated by a 
drawing made with the aid of a camera lucida. 
