Kossel, in fact, decomposed the nuclein by a series of very carefully arranged operations, and has reduced it step by step to its crystallizable organic radicals. At each stage that we descend in the scale of simplification a body appears which is more acid and more rich in phosphorus. At the third stage we come to phosphoric acid itself. The first operation divides the nuclein into two substances: the new albumin and nucleinic acid. After separating these elements they can be reunited: a solution of albumin with a solution of nucleinic acid reconstitutes the nuclein. A second operation separates the nucleinic acid in its turn into three parts. One is a body of the nature of the sugars—_i.e._, a carbohydrate. The appearance of a sugar in this portion of the molecule of nucleinic acid is an interesting fact and fertile in results. The second part is constituted by a mixture of nitrogenous bodies, well known in organic chemistry under the name of _xanthic bases_ (xanthin, hypoxanthin, guanin, and adenin). The third part is a very acid body and full of phosphorus—thymic acid. If in a third and last operation the thymic acid is analyzed, it is finally separated into phosphoric acid and into thymene, a crystallizable base, and thus we are brought back to the physical world, for all these bodies incontestably belong to it. § 3. THE CONSTITUTION OF HISTONES AND ALBUMINS. _Constitution of Histones._—But we are only half-way through our task. We are acquainted in its origin with one of the genealogical branches of the proteid, the nucleinic branch. We must also learn something of the other branch, the albumin or histone branch. But on this side the problem assumes a character of difficulty and complexity which is admirably adapted to discourage the most untiring patience. The analysis of albumin for a long time baulked the chemist “Here,” said Danilewsky, “we come to a closed door which resists all our efforts.” We know how vastly interesting what is taking place on the other side must be, but we cannot get there. We get a mere glimpse through the cracks or chinks which we have been able to make. This analysis of albuminous matter at first requires great precautions. The chemist finds himself in the presence of architecture of a very subtle kind. The molecule of albumin is a complex edifice which has used up several thousand atoms. To perceive the plan and structure, it must be dismantled and separated into parts which are neither too large nor too small. Such careful demolition is difficult. Processes too rough or too violent will reduce the whole to the tiniest of fragments. It is a statue which may be reduced to dust, instead of being separated into recognizable fragments, easily fitted in place along their fractured faces.