448 The Islands of Langerhans in the Human Embryo 
by Mall (12). Series from a catalogued collection are indicated by a 
number in Roman characters placed after the name of the possessor. 
1. Prof. Mall (No. XXII), Baltimore, length 20 mm., probable age 47 days. 
2. 6 «6 (No. XLV), 6 OB sh). G6 “ Ge apie. Gt 
5. Dr. Longeope, Philadelphia, GG eniays ar be G5 968}. 00 
ASE ce a a as 60 «&< «c 6c Se ce 
5. Prof. Mall (No. XLIV), Baltimore, eT Oi ve 66 Same: Se 
65 «= (No. XXIII), Baltimore, CO mance v6 se 840 
ec «© 6 (No. XXXIV), CSO rcs 66 co SO 
8. ‘ Marchand, Leipzig, CO OO bree 6 tC “947 ec 
9. ‘ Mall, Baltimore, CeO ane’ 6 Ga {hh SC 
10. ‘+ Marchand, Leipzig, no measurement, supposed ‘ 3 months. 
11. Dr. Longeope, Philadelphia, length 115 mm., probable ‘* 115 days. 
12. Prof. Mall, Baltimore, COAG ence & CCUG G merce 
13. Dr. Longcope, Philadelphia, uG az 168 “6 Se Ry 86 
14. Prof. Mall (No. XLVIII), Baltimore, G3 - F1B0). =. GG “ ce- 720 «& 
15. Dr. Longcope, Philadelphia, “6-145 66 66 CCE DCE 
lays UC ac ee “ 160) << “ ce GOR 
Mfte, | 9BC cc “ « 160 & ve “160 ¢& 
18. Prof. Mall, Baltimore, GE AGO) BC we COMO Mea 
19. Dr. Longceope, Philadelphia, be PANO oC te sc 200 = «% 
20. Prof. Mall, Baltimore, 205) «& “ 6 205, & 
21. ‘* Marchand, Leipzig, cc 210 ss es coy 210 ass 
The earliest stage studied (Nos. 1 and 2) was that in which the glands 
are represented by branching processes widely separated by a rich frame- 
work of connective tissue. The connective tissue is about equal in 
amount to the glandular portion of the organ, and is the most striking 
feature throughout the early stages of development. It disappears 
‘slowly but even in the fifth and sixth months of foetal life still arrests 
the attention. Its presence is of great assistance, for it marks off the 
anatomical units of the pancreas in a way that greatly facilitates their 
study. Each group of cells is thus distinctly separated from neighbor- 
ing groups, rendering the study of such a group in serial sections possi- 
ble and easy. This anatomical condition made it very easy, as will be 
shown, to trace the relation of an island to its acinus. In this early 
stage it was not possible to find any arrangement of cells suggestive of 
the formative stages of the islands, nor was it possible to find the pecu- 
har cells with rich eosinophile protoplasm which Laguesse and Renaut 
compare to the parietal or oxyntic¢ cells of the gastric tubules, and which 
they consider to be the earliest differentiation of cells destined to form 
islands. 
In the next preparation (No. 3), from an embryo 54 mm. in length, 
the early development of the islands can be easily seen. The freshness 
