The Histochemical Recognition, of Lipine

The purpose of the investigation described in this paper was to find a rigorous and sensitive histochemical colour-test for the demonstration of lipine in plant and animal tissues. Full details are given of two new tests, called the acidhaematein and the pyridine-extraction tests. The presence of lipine is reliably indicated by the use of the two tests in conjunction. The acid-haematein test is derived from that of Smith and Dietrich, but unlike the latter gives a positive reaction with pure lecithin. It is also much more sensitive. Diverse organic compounds that occur in the tissues of plants and animals were deposited on paper and subjected to the acid-haematein test. The test was shown to be negative to members of all the groups of such substances that were studied, except lipines and certain proteins. The pyridine-extraction test serves to separate the positive reaction with lipines from that with certain proteins. Its validity was proved by experiments on known substances deposited on paper. In the pyridine-extraction test, tissues are extracted with hot pyridine before subjection to the aeid-hamnatein test. The tendency for certain proteins to give a positive reaction is now somewhat increased, while lipines are wholly negative. Any organic substance that reacts positively to the acidhaematein test but negatively after pyridine extraction consists of or contains lipine. Mitochondria are among the tissue-constituents that are shown by the tests to contain lipine. It has long been regarded as probable that they do so ; but they respond negatively to the Smith-Dietrich test, and there has not previously been rigorous proof by any in situ histochemical method that they do in fact contain lipine.