Was there ever a single collection of the Corpus Juris Civilis and has it survived?

No. It did not survive.

That is, it seems self-evident that at the source Justinian and his lawyers would have had a single book-shelf filled with the entire collection? But after that it gets complicated and sketchy for quite some time.

From its creation until centuries later the number of manuscripts used, compiled, in circulation was indeed quite manifold. Not least because of its sheer size. No 'original edition' survives and the very concept "corpus" indicates a small library of texts.

The surviving manuscripts are of course fragmentary the older they get and different parts of this corpus had a very markedly different popularity, leading to a different rate of adoption in various parts of the Byzantine Empire – with Italy being sufficiently divergent at the time to take the longest – and otehr parts of the old Roman world and after. As the Byzantine sphere of direct control retracted again, the spread of Justianianic texts slowed down even further.

Only in the high middle ages can we see renewed interest and rediscoveries that slowly lead to more comprehensive collections – of parts – that glacially approached a somewhat canonical edition of original material that by then had to be partially reconstructed already.

even if Aristotle’s Posterior Analytics had never been found. But it is unthinkable that a science of law could have taken shape in the medieval West without the rediscovery of Justinian’s Digest, about 1070 AD. The central monument of ancient Roman jurisprudence presented a model and a challenge to the medieval mind for which the eleventh-century reader was rather ill-prepared. To be sure, relics of the imposing structure of the laws of Rome existed … Lombard Italy and the formerly Byzantine regions of the peninsula had preserved portions of Justinian’s Code (Codex Justinianus), his elementary Institutiones, and an abridged Latin version of his Greek Novellae (the Epitome Juliani).
_{–– Stephan Kuttner: "The Revival of Jurisprudence", in: Renaissance and Renewal in the Twelfth Century, ed. by Robert L. Benson and Giles Constable (Cambridge, Mass., 1982), pp. 299–300.}

The errors for Bamberg Jur. 1, Turin D.III.13, and Paris 4421 have already been noted, and the same tendency toward excessively early attributions can be seen in the other manuscripts Krüger listed. The Monte Cassino manuscript, which was reconstructed out of leaves later used to bind other manuscripts, today is more correctly attributed to the second half of the eleventh century. Vercelli 122, a manuscript of the Epitome Juliani of the Novels with excerpts of the Institutes and the Code, turns out to be another manuscript in minuscula romanesca, which Supino attributed to the mid-eleventh century. In contrast, the datings for Bamberg Jur. 2 and Cologne 328 change little: the Bamberg manuscript would be more properly described as XIex./XIIin., that is, within 25 years of 1100, while Cologne 328 is perhaps slightly later, from the early twelfth century. The attribution of the Verona fragment to the sixth century and the Berlin excerpt to the ninth are correct.

Even as Krüger was finishing his edition of the Institutes, he was turning his attention to Justinian’s Code. This work posed far more complex problems than the rest of Justinian’s codification. Except for a lengthy but still very partial palimpsest preserved at Verona, there were no ancient manuscripts comparable to F that might anchor an edition. Nor were the manuscripts from the medieval universities as complete as those of the Institutes, for they omitted all constitutions in Greek, most of the inscriptions and subscriptions stating the legislative circumstances for the individual laws, and books nine through twelve (which were transmitted separately as the Tres Libri). Nor was it even apparent how the vulgata manuscripts related to one another — an essential point for the Lachmann method — since they did not even agree on the order of presenting the constitutions. Krüger concluded that the university-era manuscripts, rather than having a direct lineage with antique manuscripts, instead derived from a shortened version of the Code, known as the Epitome Codicis, that survived in a handful of earlier manuscripts: evidently medieval scholars had taken the Epitome as a base text, reinserting previously omitted materials until they had reconstructed (with some errors) Justinian’s original text. He proposed, therefore, to concentrate on the manuscripts of the Epitome Codicis, relying on a small selection of the earliest manuscripts of the restored version to fill in the missing details.

The earliest evidence for the Epitome Codicis, therefore, is no earlier than the mid-eleventh century — the period of the earliest manuscripts and when it began to be used by Lombardist jurists. It is, indeed, to them that the creation of the Epitome must be ascribed. For them, as for no other group since the sixth century, the legal language of the Code would not have posed an insurmountable obstacle: experienced in applying and teaching law, they would have understood how important it was to preserve the precise language of every enactment. As laymen who lacked access to a monastic scriptorium, and who seem often to have copied books for their own use, they also would have needed something shorter than the original. In contrast to the Institutes, Justinian’s Code is an enormous work. The first nine books of the Code total roughly 340,000 words, while all twelve contain 420,000 words. Such magnitudes dwarf the other books used by these jurists: the Liber Legis Langobardorum without glosses is less than 60,000 words, about the size of Justinian’s Institutes, while the Walcausina with its extensive glosses totals just under 100,000 words. Seen in this context, extracting the constitutions of the greatest interest or with the most important practical implications represented a reasonable compromise between the intellectual interests of the jurists and the resources available to them for copying books in the middle decades of the eleventh century.

The manuscripts discussed in this book include several that rank among the most challenging of all medieval manuscripts. Written by multiple scribes, some of whom had elementary abilities or wrote with documentary scripts, manuscripts such as the Pistoia Epitome, Berlin 273, or even — in other ways — the Vat. lat. 1406 pose exceptional problems to anyone attempting to understand when, how, and by whom they were produced. One cannot be surprised that nineteenth-century scholars made mistakes dealing with them. It is less easy to understand how their errors came to be perpetuated so long. The absence of citations should have been a warning to anyone who thought about it: works that are studied are cited, even in the Middle Ages. In fact, as we have seen, the works of Justinian’s Corpus—with the exception always of the Novels—were virtually unknown between the sixth and the eleventh centuries. Early medieval manuscripts of these works amount to no more than two fragments of the Institutes, one of which also contained an unknown quantity of the Digest; not even that much survives for the Code. Evidence that these works were discussed at all is hardly more substantial, consisting mainly of a few unsystematic collections and a handful of elementary citations, mainly in papal letters from the third quarter of the ninth century.

This situation began to change only in the late tenth and early eleventh century. Indications that the Justinianic books were starting to find readers come from a number of directions: a few arengae from Ravenna, the Summa Perusina in and around Rome, the Bamberg Institutes, again from Rome. A different level of engagement, however, is apparent in the increasingly expert references to the Corpus found in the works of the professional jurists centered on the old Lombard capital of Pavia. One sees the use of the Institutes already in the generation of Bonifilius, whose first appearance in the documentary record comes from the 1010s; by the 1040s the Code had also been taken up; and while it is harder to be certain about the Digest a date around mid-century could not be far off. To judge from citations of the Corpus, such as the Marturi plea or the glosses in the Expositio and Walcausina, these studies went beyond collecting maxims and definitions to a systematic examination of Roman rules and procedures.

The role of these legal professionals in the history of Justinian’s works goes a long way toward explaining some of the most unusual features of the manuscripts. As laymen lacking ready access to organized scriptoria and large numbers of trained copyists, these early jurists often had to copy books themselves—either individually or in groups. The longest of Justinian’s texts, the Code and the Digest, were several times longer than the Lombard laws even with their commentaries: so long that they may simply have overtaxed the means for producing books for study. In response to this problem, the judges contented themselves with the Epitome Codicis, a collection of the laws most important to them that was expanded over time as new materials were extracted by return visits to the ancient manuscripts. We saw in chapter six that something similar may also have been done with the Digest.

The key text in this early period seems to have been the Code. Although it is a text that can seem sterile to us, eleventh-century jurists seem to have found endless fascination in it, perhaps in part because as a compendium of legislation it corresponded so closely to their manuscripts of Lombard law. It is the most cited work in the Expositio and the work for which we possess the greatest number of early manuscripts. The manuscripts also capture the intensity of scholarly work applied to the Code: the layers on layers of supplements and glosses that upwards of 40 hands applied to the Pistoia Epitome Codicis within a few decades; the multiple reconstructions of the integral Code, witnessing the efforts of groups in different regions; the fifteen copyists of Berlin ms. 273; the daring recasting of the entire format of the text represented by Montpellier ms. 82. The lack of interest in the history of the Code in the eleventh century must therefore be counted among the most serious failures of historians dealing with the juristic renaissance.

Given the feverish study of Justinian’s texts in the third quarter of the eleventh century, it is not surprising the discipline itself soon underwent a significant transformation. The restoration of the Code and the first manuscripts of the Digest both seem to date from the 1070s and 1080s. No less significant, perhaps, is the absence of work dedicated to the Lombard law that can be attributed to the 1080s or later. Taken together, these trends suggest that the energy, expertise, and personnel which had developed in previous decades was turning more exclusively to Roman law, the “hot topic” of the moment. As is typical with anything concerning the history of legal studies, too little narrative evidence survives for us to be able to trace this process in any detail: these were not men who wrote about themselves or each other, and the earliest surviving efforts to tell the story of these events were the self-serving and mythologizing comments of thirteenth-century Bolognese masters. Yet for our more limited purpose of tracing the history that created the medieval texts of Justinian’s books, the decades around 1100 marks an appropriate conclusion. Later scholars continued to suggest emendations and note collations, and it may not have been until the mid-twelfth century that the separation of the Tres Libri from the Code and the divisions of the Digest were completely stable. But they were working with texts that derive directly from manuscripts similar to those discussed in this book, and within a disciplinary context that had largely taken shape in the second half of the eleventh century.

_{–– Charles M. Radding & Antonio Ciaralli: "The Corpus Iuris Civilis in the Middle Ages. Manuscripts and Transmission from the Sixth Century to the Juristic Revival", Brill’s Studies in Intellectual History 147, Brill: Leiden, Boston, 2007.}