The yam is a tuber of the genus Dioscorea, a group of climbing plants indigenous to tropical climates. It is oblong and in some cases grows to a length of 3 ft. It may weigh as much as 30lbs. It contains a large proportion of starch. When boiled or roasted it forms a mealy, palatable and wholesome food. It is not sweet like the sweet potato and keeps better. A species brought from China to France is still cultivated there., supplying a vegetable of a starchy sort all the year round.
Some species of yam are poisonous. Church gives the approximate composition as follows:
From The Baker’s ABC by John Kirkland, formerly Head Teacher of National School of Baking, published 1927 by Gresham
The Vintage Cookbook Trials 
Albumin must be an old term for protein.