The law is, however, imperfectly enforced for financial reasons.
At that date the science of chemistry was very imperfectly known, and the real constituents of ordinary remedies so little understood that different virtues were attributed to different products containing the same constituents.
The specific effects of different impurities on the physical properties of zinc have only been imperfectly studied.
Even here, however, general agreement has not ~en reached; and the questions involved in relating the facts the distribution of plant communities to the factors of the tbitat are very imperfectly understood.
Woody or lignified cell-walls appear to contain substances called conifer-in and vanillin, in addition to various other compounds which are imperfectly known.