There are two distinct manuscripts in the world of academic journal: solicited and unsolicited manuscripts. Solicited manuscripts, of course, are relatively valuable things and the authors creating them have been asked by academic journals to create said manuscripts. Unsolicited manuscripts, by contrast, are created by authors based on their own research.
Publishers Typically Solicit Manuscripts
Authors and researchers published in the past by academic journals frequently benefit from solicitation of new manuscripts by those same publishers. Authors and researchers whose priors works have proven popular, either by citation in other media sources such as journals, magazines, and so forth also produce a higher amount of solicited manuscripts. After all, why wouldn’t you research and then write a manuscript if you knew it was wanted by a publisher?
Most publishers, in fact, regularly solicit manuscripts or at least issue calls or requests for manuscripts, examine initial treatments by authors and then give them the go-ahead (or a rejection, on the other hand) allowing for many solicited manuscripts to at least enter the preliminary or early stages of book and article publishing. In fact, some publishers only accept solicited manuscripts from authors, typically those with literary or other publishing agents with some influence at various publisher.
Publishers Accepting Unsolicited Manuscripts
All is not lost for unsolicited manuscripts, however, for some publishers actually do accept unsolicited creations and even give them more than just a cursory glance before consigning them to the rejection bin. Some publishers even believe in accepting only unsolicited manuscripts. This is perhaps on the theory that an unsolicited manuscript’s author is hungry, would be amenable to extensive rewrites from copy editors and would generally jump as high as the publisher said to jump, and at the scheduled intervals.
Of course, finding a publisher willing to accept an unsolicited may take some time and effort. Very small boutique publishers or publishers of obscure journals are sometimes willing to take a chance on an unsolicited manuscript. Of course, such publishers and journals may have very little influence and even less in the way of resources to ensure an author’s work receives the distribution and recognition it deserves. This is also another reason for why large publishers may not consider an unsolicited article or manuscript: they’re sometimes inundated with them, by authors of both great skill as well as those with very little.
In the end, if you have a manuscript and no publisher has asked you to create it you must become your own best salesman, agent’s assistant (or even the agent himself), publicist and all-around pest to a publisher. It will take some effort to see your unsolicited manuscript accepted by a publisher, but more than a few of the best works created by authors started out in such a manner. If on the other hand, you have a publisher soliciting manuscripts, especially of the type you create, then the world is your oyster, though it may be a very small oyster at least at the beginning. But your publisher, upon gazing at the magnificent edifice that is your solicited manuscript, will no doubt turn it into an immortal and renowned work.