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RICHARD E. SCAMMON 



plane where the anterior lobe of the liver joins with the two lateral 

 and posterior ones. The two lateral lobes form the third seg- 

 ment (C to D). The first segment, A to B, was divided into 

 three equal parts and the sections falling upon the planes separat- 

 ing these parts {1 and 2) were used for measurement. Two 

 sections were selected in the same manner from the second seg- 

 ment B to C. The third segment C to D was divided into five 

 equal parts and the four sections falling on the dividing planes 



Fig. 13 Diagram of the liver of an Acanthias embryo showing method of 

 selecting sections for measurements of the blood vessels. Bile ducts and gall 

 bladder represented in black. 



used for measurement. In this segment only the left lobe was 

 measured in each case. The sections thus determined were 

 drawn with the camera lucida or projection apparatus and the 

 total area, the total area of the vascular bed in cross-section, and 

 the area of the larger vascular trunks in cross-section were then 

 determined by means of a planometer.^ From this data the 

 figures given in table 2 were calculated. Such a method can lay 

 no claim to great accuracy. The possibility of error is quite 

 large and the method of determining the position of the sections 

 has some objections, for all parts of the liver do not grow at the 



* It is impossible to determine the exact area of the large trunks in the earlier 

 stages because of their great irregularity and their many connections with the 

 adjoining sinusoids. In embryos 20 to 21 mm. long the area of the main venous 

 trunks forms about 20 per cent of the entire cross section area of the vascular 

 spaces of the liver. This drops to about 15 per cent in embryos of 25 to 28 mm. 

 and increases thereafter with the relative reduction of the sinusoids. In the last 

 member of the series in table 2, the main trunks formed about 30 per cent of the 

 total cross section area of the blood vessels. 



