(Ac 4'") ; yet this is but the technical description (a.ypa.|x^laTOl. kolI i5i(I)Tai) of men who had not gi'adu- ated in the colleges of the scribes. If not many noble were called (1 Co l-*), there were at least some who combined sjnritual insight with literary culture, and who were able to express the new ideas in forms whose beauty is partially hidden by their Divineness.
Of Jesus Himself His enemies asked (Jn 7'*), ' How knoweth this man letters (ypafjifiara), having never learned?' No doubt it Avas true that He had never studied Jewish theology at any of the great Rabbinical schools. But not only did He have a thorough knowledge of the letter of the OT, as He repeatedly showed (see, e.g., Mt 5-'""" josff- -wfT. 131-"- 15^- "'• ig-iff- I'ff- 21'^' ^®' *^ 22*-* ^*- '*^^- 2413. 37ff. 26*^ •27-^), but He revealed an insight into Scripture and an expository skill (and this was what the Jews specially meant by His ' knowing letters') at which they were compelled to marvel ( Jn 7'*'). This ' learning ' of Jesus, for ypd/jLuara in Gr. (like Lat. litcra', Eng. 'letters') is synonymous with ' learning,' had it-s human side without doubt. His education in Scripture would begin in the family circle, and most probably be continued in a sj'nagogue school. In early youth He showed His interest in the sj-nagogal instruction (Lk 2^), and ever afterwards it was His 'custom' to fre(|uent those services of the synagogue at which Moses and the Prophets were read and explained (Lk -4'^). But His ' learning ' and consequent ' teaching,' on the spiritual side, as He Himself declared, came from an inward and Divine spring (Jn 7^''- ''), a saj-ing which helps to explain the statement of two of the Sj-noptists (Mt 7-'^ Mk 1-), ' He taught them as one having authority, and not as the scribes ' (ypafjifiaTeis). See also art. EDUCATION'.
LiTER.\TrRK.— Hastingrs' DB. art. ' Education ' ; Schiirer. lUP n. i. 3-23-350, ii. 47-52 ; Edersheini, Life and Timts, i. 22S-234 ; Stalker, Imago Christi, pp. 147-164. R. SCOTT.
LEAYEN. — The eflect of leaven u]X)n doiigh to which it is added is due to minute living organisms disseminated through it in great numbers. These organisms are one or more species of yeast-fungi. They are the most imijortant agents of the alcoholic fermentation, which they produce in dough as well as in solutions of sugar. Whether lodged in sour dough (leaven) or collected free out of fermenting vats (compressed yeast), they cause the same eti'ect when introduced into bread sponge. At the pre- sent tijiie leaven is not so much used for the light- ening of bread as yeast, because it is apt to impart to bread a sour taste and a disagreeable odour.
Yeast-f un^i were first recognized (16S0) by the Dutch naturalist Leuwenhock in the scum floating; on the surface of fermenting beer. With his imperfect lenses he was able to observe little of their structure beyond the fact that they were very small globules. They are now known to be single - celled plants, having for the most part an oval or ellipsoidal shape. The in- dividual yeast-cell consists of a mass of protoplasm enclosed in a delicate wall of cellulose. The protoplasm, as in the case of all the fungi, contains no chlorophyll, and is, accordingly, dependent upon organic matter for its nourishment. It is granular, and usually shows one large non-contractile vacuole or several small vacuoles containing water. It has also a nucleus, which, however, can be brought into view only after special treatment The size of the yeast-cell varies from I'o microns to 15 microns in diameter. (Tlie micron equals .j.^.-i,-, inch). During the inactive stage the cells are isolated, but in an actively fermenting medium they occur in groups or families, organically united and consisting of from two to six or eight members in varying stages of development. When the mem- bers reach maturity, they separate from one another, each one having the capacity to produce a new group. This is the method by which the plant propagates itself. An isolated cell sends out a little pimple or bud on the surface. The bud is destined to become an independent cell of the same size as the cell which produced it ; but, before it is mature, it may itself form a bud which in turn may form another bud of its ovm. the mother-cell m the meantime forming a second bud at a different point. A sort of chain of sprouts, usuallj' curved, is formed as the result of this process of buddinff or oeinmatinn. The suc- cessive buds round up and finally separate themselves as in-
'^'9
LEAVES
LEEEyEUS
dependent individuals. Pasteur, to whose elaborate investiga- tions we are deei^lj' indebted for our knowledge of the agents and the process of fermentation, found that two cells produced eight in two hours at a temperature of 13 degrees C. The multiplication is more rapid at a higher temperature.
Yeast-fungi secure their food for the most part from weak solutions of grape-sugar. They convert grape-sugar into alcohol and carbon dioxide. This conversion is known as the alcoholic fermentation. The same action takes place in moistened wheat- flour when yeast is mixed with it. The wheat grain contains a ferment, diastase, whose function is the conversion of the in- soluble starch of the grain into soluble grape - sugar for the nourishment of the embryo when the grain germinates. Dias- tase is present, of course, in wheat-flour, and when the condi- tions of moisture and temperature are supplied, as in a gently heated bread sponge, it effects the same conversion as under natural conditions in the germinating grain. Some of the flour starch is changed into grape-sugar, in which the yeast-cells excite the alcoholic fermentation. The bubbles of the gas carbon dioxide produced in the fermentation are entangled in the glutinous sponge, and, expanded by heat, puff it up or lighten it. If, now, more flour is thoroughly mixed with this sponge so as to scatter the yeast-cells of the sponge throughout the mass, the whole vnW shortly be leavened by the gas which continues to be given off by the agency of the rapidly multiply- ing cells. A practically indefinite quantity of flour so treated can be leavened by 'a little leaven.'