The means of production on the one hand, labour-power on the other, are merely the different modes of existence which the value of the original capital assumed when from being money it was transformed into the various factors of the labour-process. That part of capital then, which is represented by the means of production, by the raw material, auxiliary material and the instruments of labour does not, in the process of production, undergo any quantitative alteration of value. I therefore call it the constant part of capital, or, more shortly, constant capital.
On the other hand, that part of capital, represented by labour-power, does, in the process of production, undergo an alteration of value. It both reproduces the equivalent of its own value, and also produces an excess, a surplus-value, which may itself vary, may be more or less according to circumstances. This part of capital is continually being transformed from a constant into a variable magnitude. I therefore call it the variable part of capital, or, shortly, variable capital. The same elements of capital which, from the point of view of the labour-process, present themselves respectively as the objective and subjective factors, as means of production and labour-power, present themselves, from the point of view of the process of creating surplus-value, as constant and variable capital.
A part of capital has been advanced in the form of constant capital, i.e., of means of production, which function as factors of the labour-process so long as they retain the independent use-form in which they enter this process. The finished product, and therefore also the creators of the product, so far as they have been transformed into product, is thrust out of the process of production and passes as a commodity from the sphere of production to the sphere of circulation. But the instruments of labour never leave the sphere of production, once they have entered it. Their function holds them there. A portion of the advanced capital-value becomes fixed in this form determined by the function of the instruments of labour in the process. In the performance of this function, and thus by the wear and tear of the instruments of labour, a part of their value passes on to the product, while the other remains fixed in the instruments of labour and thus in the process of production. The value fixed in this way decreases steadily, until the instrument of labour is worn out, its value having been distributed during a shorter or longer period over a mass of products originating from a series of constantly repeated labour-processes. But so long as they are still effective as instruments of labour and need not yet be replaced by new ones of the same kind, a certain amount of constant capital-value remains fixed in them, while the other part of the value originally fixed in them is transferred to the product and therefore circulates as a component part of the commodity-supply. The longer an instrument lasts, the slower it wears out, the longer will its constant capital-value remains fixed in this use-form. But whatever may be its durability, the proportion in which it yields value is always inverse to the entire time it functions. If of two machines of equal value one wears out in five years and the other in ten, then the first yields twice as much value in the same time as the second.
This portion of the capital-value fixed in the instrument of labour circulates as well as any other. We have seen in general that all capital-value is constantly in circulation, and that in this sense all capital is circulating capital. But the circulation of the portion of capital which we are now studying is peculiar. In the first place it does not circulate in its use-form, but it is merely its value that circulates, and this takes place gradually, piecemeal, in proportion as it passes from it to the product, which circulates as a commodity. During the entire period of its functioning, a part of its value always remain fixed in it, independently of the commodities which it helps to produce. It is this peculiarity which gives to this portion of constant capital the form of fixed capital. All the other material parts of capital advanced in the process of production form by way of contrast the circulating, or fluid, capital.
Some means of production do not enter materially into the product. Such are auxiliary materials, which are consumed by the instruments of labour themselves in the performance of their functions, like coal consumed by a steam-engine; or which merely assist in the operation, like gas for lighting, etc. It is only their value which forms a part of the value of the products. The product circulates in its own circulation the value of these means of production. This feature they have in common with fixed capital. But they are entirely consumed in every labour-process which they enter and must therefore be wholly replaced by new means of production of the same kind in every new labour-process. They do not preserve their independent use-form while performing their function. Hence while they function no portion of capital-value remains fixed in their old use-form, their bodily form, either. The circumstance that this portion of the auxiliary materials does not pass bodily into the product but enters into the value of the product only according to its own value, as a portion of that value, and what hangs together with this, namely, that the function of these substances is strictly confined to the sphere of production, has misled economists like Ramsay (who at the same time got fixed capital mixed up with constant capital) to classify them as fixed capital.
That part of the means of production which bodily enters into the product, i.e., raw materials, etc., thus assumes in part forms which enable it later to enter into individual consumption as articles of use. The instruments of labour properly so called, the material vehicles of the fixed capital, are consumed only productively and cannot enter into individual consumption, because they do not enter into the product, or the use-value, which they held to create but retain their independent form with reference to it until they are completely worn out. The means of transportation are an exception to this rule. The useful effect which they produce during the performance of their productive function, hence during their stay in the sphere of production, the change of location, passes simultaneously into the individual use in the same way in which he pays for the use of other articles of consumption. We have seen that for instance in chemical manufacture raw and auxiliary materials blend. The same applies to instruments of labour and auxiliary and raw materials. Similarly in agriculture the substances added for the improvement of the soil pass partly into the plants raised and help to form the product. On the other hand their effect is distributed over a lengthy period, say four or five years. A portion of them therefore passes bodily into the product and thus transfers its value to the product while the other portion remains fixed in its old use-form and retains its value. It persists as a means of production and consequently keeps the form of fixed capital. As a beast of toil an ox is fixed capital. If he is eaten, he no longer functions as an instrument of labour, nor as fixed capital either.
What determines that a portion of the capital-value invested in means of production is endowed with the character of fixed capital is exclusively the peculiar manner in which this value circulates. This specific manner of circulation arises from the specific manner in which the instrument of labour transmits its value to the product, or in which it behaves as a creator of values during the process of production. This manner again arises from the special way in which the instruments of labour function in the labour-process.
We know that a use-value which emerges as a product from one labour-process enters into another as a means of production. It is only the functioning of a product as an instrument of labour in the process of production that makes it fixed capital. But when it itself only just emerges from a process, it is by no means fixed capital. For instance a machine, as a product or commodity of the machine-manufacturer, belongs to his commodity-capital. It does not become fixed capital until it is employed productively in the hands of its purchaser, the capitalist.
All other circumstances being equal, the degree of fixity increases with the durability of the instrument of labour. It is this durability that determines the magnitude of the difference between the capital-value fixed in instruments of labour and that part of its value which it yields to the product in repeated labour-processes. The slower this value is yielded — and value is given up by the instrument of labour in every repetition of the labour-process — the larger is the fixed capital and the greater the difference between the capital employed in the process of production and the capital consumed in it. As soon as this difference has disappeared the instrument of labour has outlived its usefulness and has lost with its use-value also its value. It has ceased to be the depository of value. Since an instrument of labour, like every other material carrier of constant capital, parts with value to the product only to the extent that together with its use-value it loses its value, it is evident that the more slowly its use-value is lost, the longer it lasts in the process of production, the longer is the period in which constant capital-value remains fixed in it.
If a means of production which is not an instrument of labour strictly speaking, such as auxiliary substances, raw material, partly finished articles, etc., behaves with regard to value yield and hence manner of circulation of its value in the same way as the instruments of labour, then it is likewise a material depository, a form of existence, of fixed capital. This is the case with the above-mentioned improvements of the soil, which add to it chemical substances whose influence is distributed over several periods of production or years. Here a portion of the value continues to exist alongside the product, in its independent form or in the form of fixed capital, while the other portion of the value has been delivered to the product and therefore circulates with it. In this case it is not alone a portion of the value of the fixed capital which enters into the product, but also the use-value, the substance, in which this portion of value exists.